AURORA, Colo. – Police say they believe the suspect in a deadly shooting at a Colorado movie theater planned the attack with "calculation and deliberation," as they removed all explosives from his booby trapped apartment.
The suspect, James Holmes, is accused of going on a shooting rampage at the movie theater during Friday's midnight showing of "The Dark Knight Rises," killing 12 people dead and injuring 58. He was packing as many as 6,000 rounds of ammunition with the ability to shoot up to 50 a minute, police said.
Fox News has learned a possible second person of interest in the case is also being investigated, though sources caution authorities are not yet sure if the individual is necessarily tied to the crime.
In a statement to Fox News early Sunday, the Aurora Police Department confirmed an "associate" of Holmes had been interviewed in relation to the case, but at this time they do not believe he was involved.
The person who owns the home where the reported person of interest lives tells FoxNews.com investigators are looking for his tenant because they have interviewed all students from Holmes's program and his tenant is the only one who they haven't been able to reach. However, the landlord said he believes the tenant has been in Korea for "weeks."
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Earlier Saturday, authorities eliminated all the explosives in Holmes' booby-trapped apartment. No officials were injured in the process.
Aurora police Sgt. Cassidee Carlson says the booby trap trip wire at his apartment was "meant to kill," the first person who opened the door to the apartment.
The Aurora police chief says the trap was meant specifically to kill a police officer who might have opened the door.
"We sure as hell are angry," Chief Dan Oates said about the trap being aimed at officers. Oates also apparently tried to head off a mental incompetence defense by saying Holmes was deliberate and calculating in receiving numerous commercial deliveries to his home and workplaces over the past four months.
"This is some serious stuff that our team is dealing with," Sgt. Carlson said. Witnesses have reported hearing two small booms during the disarming process.
Holmes' apartment was loaded with explosives and authorities say they will not know for sure what is inside until they enter and test results come back from an FBI lab. A robot was sent in to disarm and diffuse the major threats as well as remove evidence.
Initial attempts to enter the apartment Friday were unsuccessful. The FBI, ATF and local authorities are working together to enter the apartment.
"There are still unknowns, we're not exactly sure of everything that's in there," Sgt. Carlson said. The unknown includes jars that are believed to contain accelerates. Authorities say there are balloons filled with gun powder and bullets littered throughout the floor.
The first phase, which according to officials was successful, was to render the area safe and address the immediate threat of the wire trip booby trap. The public had been warned that parts of these phases may cause loud booms and have planned for reverse 911 calls for the area so that the public may remain informed.
The second phase will be to dispose of the aerial shells which will include placing the devices into sand trucks and taken to a disposal site for a controlled detonation. Authorities believe there may be up to as many as 30 shells.
The third phase will be the investigation of the apartment itself.
"There is no timeline, there is no end time,” Sgt. Carlson said. "We don't need to rush anything," she said.
Authorities said Saturday that they hope to begin allowing residents back into their homes by Sunday. They also said they hope to finish with the investigation at the movie theater by Monday, with the goal of handing the theater back to the owners by Wednesday.
Relatives of two of the twelve dead confirmed late Friday that their loved ones were killed during the midnight showing of "The Dark Knight Rises."
The family of Alex Sullivan issued a statement confirming his death. He died on his 27th birthday.
Twenty-three-year-old Micayla Medek was also among the dead.
Her father's cousin, Anita Busch, says the sad news at least brought peace to the family.
The brother of Jessica Ghawi previously confirmed his sister's death.
"He looked like an assassin ready to go to war," said Jordan Crofter, a moviegoer who was unhurt in the attack early Friday, about a half-hour after the special midnight opening of "The Dark Knight Rises."
Holmes, used a military-style semi-automatic rifle, a shotgun and a pistol, stopping only to reload.
The suspect marched up the aisle in the stadium-style theater, picking off those who tried to flee, witnesses said. Authorities said he hit scores of people, with a few of the 70 victims suffering their injuries not by gunfire but in the ensuing chaos. At least one person was struck in an adjacent theater by gunfire that went through the wall.
"He would reload and shoot and anyone who would try to leave would just get killed," said Jennifer Seeger, adding that bullet casings landed on her head and burned her forehead.
Within minutes, frantic emergency services calls brought some 200 police officers, ambulances and emergency crews to the theater. Holmes was captured in the parking lot and remains in police custody. Police said they later found that his nearby apartment was booby-trapped.
Authorities gave no motive for the attack. The FBI said there was no indication of ties to any terrorist groups.
In New York City, Police Commissioner Raymond Kelly said: "It clearly looks like a deranged individual. He has his hair painted red. He said he was the Joker, obviously the enemy of Batman."
It was the worst mass shooting in the U.S. since the Nov. 5, 2009, attack at Fort Hood, Texas. An Army psychiatrist was charged with killing 13 soldiers and civilians and wounding more than two dozen others.
It was the deadliest in Colorado since the Columbine High School massacre in suburban Denver in 1999, when two students killed 12 classmates and a teacher and wounded 26 others before killing themselves.
The latest shooting rocked this sprawling suburb of 325,000 east of Denver. A makeshift memorial with 12 candles in a row and piles of flowers sat at a corner near the entrance to the movie theater parking lot. Up the hill from there, about 20 pastors led an emotional vigil for about 350 people, some hugging and crying
At an emotional afternoon news conference, Colorado Gov. John Hickenlooper said the people would rise above the spasm of violence, and ultimately not be "defined" by the tragedy.
The new Batman movie, the last in the trilogy starring Christian Bale, opened worldwide Friday with midnight showings in the U.S. The plot has the villain Bane facing Bale's Caped Crusader with a nuclear weapon that could destroy all of fictional Gotham.
The shooting prompted officials to cancel the red-carpet premiere in Paris, and some U.S. movie theaters stepped up security for daytime showings.
The film's director, Christopher Nolan, issued a statement on behalf of the cast and crew, expressing their "profound sorrow at the senseless tragedy."
"Nothing any of us can say could ever adequately express our feelings for the innocent victims of this appalling crime, but our thoughts are with them and their families," Nolan said.
"Words cannot express the horror that I feel. I cannot begin to truly understand the pain and grief of the victims and their loved ones, but my heart goes out to them." actor Christian Bales said in a statement.
The attack began shortly after midnight at the multiplex in Aurora. Audience members said they thought it was part of the movie, or some kind of stunt associated with it.
The film has several scenes of public mayhem -- a hallmark of superhero movies. In one scene, Bane leads an attack on a stock exchange, and in another he leads a shooting and bombing rampage on a packed football stadium.
A federal law enforcement official said Holmes bought a ticket to the show, went into the theater as part of the crowd and propped open an exit door as the movie was playing. The suspect then donned protective ballistic gear and opened fire, the official said, speaking on condition of anonymity to discuss the ongoing investigation.
At some point, the gunman appeared to have stepped outside because several witnesses saw him come through the door.
"All I saw is the door swinging open and the street lights behind, and you could see a silhouette," said Crofter, who was sitting on the left side of the theater and toward the front.
Sylvana Guillen said the gunman, clad in dark clothing, appeared at the front of the theater as the character Catwoman appeared in the movie. Then they heard gunshots and smelled smoke from a canister he was carrying.
As she and her friend, Misha Mostashiry, ran to the exit, Guillen said, they saw a man slip in the blood of a wounded woman he was trying to help.
Oates said the gunman wore a gas mask and a ballistic helmet and vest, as well as leg, groin and throat protectors. He said he bought four guns from local gun shops in the last 60 days and 6,000 rounds of ammunition, including a drum magazine that could fire 50 to 60 rounds per minute.
"My understanding is that all the weapons that he possessed, he possessed legally. And all the clips that he possessed, he possessed legally. And all the ammunition that he possessed, he possessed legally," Oates said at a press conference Friday.
Seeger said she thought it was showmanship.
"I didn't think it was real," Seeger said. She said she was in the second row, about four feet from the gunman, when he pointed a gun at her face. "I was just a deer in headlights. I didn't know what to do," she said.
Then she ducked to the ground as the gunman shot people seated behind her.
Seeger said she began crawling toward an exit when she saw a girl of about 14 "lying lifeless on the stairs." She saw a man with a bullet wound in his back and tried to check his pulse, but "I had to go. I was going to get shot."
Later, police began entering the theater, asking people to hold their hands up as they evacuated the building.
Some of the victims were treated for chemical exposure apparently related to canisters thrown by the gunman. Those hurt included a 4-month-old baby, who was treated at a hospital and released.
Authorities started to remove the bodies from the theater on Friday afternoon. Officials wheeled a black bag on a stretcher out of the front entrance, placing it in the back of a minivan. Ten people died in the theater, while two others died from their injuries later.
Those who knew Holmes described him as a shy, intelligent person raised in California by parents who were active in their well-to-do suburban neighborhood in San Diego. Holmes played soccer at Westview High School and ran cross-country before going to college.
On Friday morning, police escorted Holmes' father, a manager of a software company, from their home while his mother, a nurse, stayed inside, receiving visitors who came to offer support. Holmes also has a younger sister.
"As you can understand, the Holmes family is very upset about all of this," Lt. Andra Brown, the San Diego police spokeswoman, told reporters in the driveway of the family home. "It's a tragic event and it's taken everyone by surprise. They are definitely trying to work through this."
Police released a statement from his family that said: "Our hearts go out to those who were involved in this tragedy and to the families and friends of those involved."
There have been no indications so far that Holmes had any run-ins with the law before Friday.
Tom Mai, a retired electrical engineer, said Holmes was a "shy guy" who came from a "very, very nice family."
Holmes graduated from University of California, Riverside, in the spring of 2010 a bachelor's degree in neuroscience, a school spokesman said. Mai said the mother told him Holmes couldn't find a job after earning a master's degree and returned to school.
He enrolled in the Ph.D. neuroscience program at the University of Colorado-Denver in June 2011 but left the program last month, according to the university.
Holmes lived in an apartment in Aurora, and FBI agents and police who went there discovered it was booby-trapped when they used a camera at the end of a 12-foot pole to look inside. Authorities evacuated surrounding residences, and about two dozen people headed to a shelter set up by the Red Cross at a local school.
Holmes was in solitary confinement for his protection at a county detention facility Saturday, held without bond on suspicion of multiple counts of first-degree murder. He was set for an initial hearing on Monday and had been appointed a public defender, authorities said.
Fox News' Adam Housley and The Associated Press contributed to this report.