Park County, Colo., police on Thursday identified the gunman who took six girls hostage — killing one before turning the gun on himself — in a classroom Thursday as 53-year-old Duane R. Morrison.

Police also said armed law enforcement eventually moved in on Morrison because he was sexually "traumatizing" the victims during negotiations with police. FOX News has learned that the girls were not raped but inappropriate touching occurred.

"We have confirmed he did traumatize and assault our children ... this is why I made the decision I did. We had to go try to save them," said Park County Sheriff Fred Wegener said during a press conference. "I'll only say it's sexual in nature."

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State records showed that Morrison was arrested in July in the west Denver suburb of Lakewood on a charge of obstructing police in another suburb. He was also arrested for larceny and marijuana possession in 1973.

Reached at their home in Tulsa, Okla., Morrison's stepmother said she and her husband, Bob Morrison, "have no record of him being, having any trouble before."

"We just know the way he was raised," Billie Morrison said, declining to elaborate. She said the last time she saw him was three to four years ago.

Platte Canyon High School, where the shooting took place, remained closed Thursday as students and police gave details of the ordeal.

Morrison, who is from the Denver area and had been living in his car, apparently dressed himself like a student and walked around the school before taking any hostages.

"We knew there as kind of something wrong with the guy when we had seen him ... it's a small community where we know everybody," student Joshua Bellomy told FOX News. "He was trying to blend in with us but some of the students there tried to talk to him and knew that he was older and didn't know what was going on with him."

Morrison claimed he had explosives in a backpack and was wielding a handgun, authorities said. Police on Thursday confirmed that Morrison had at least two weapons with him. FOX News has learned that there may have been sex toys inside the backpack. Morrison released four hostages one by one, then abruptly cut off communication with authorities and set a 4 p.m. deadline that forced authorities to act.

Wegener said Morrison never said exactly what he would do when the deadline was reached. There weren't really any demands made, Wegener said, although most of what Morrison said was "leave me along, get out of here." Negotiations with police eventually tapered off, Wegener said, and as the deadline hour approached, the sheriff decided he needed to act.

Wegener said authorities used explosives as they entered the classroom, only to have the suspect fire at officers, shoot one of the girls in the head, then kill himself.

"My decision was wait ... the possibility of having two dead hostages — or act to try to save [them from] what I feared he would do to them," Wegener said. "He literally shot right at the SWAT team when they entered."

The dead victim was identified as 16-year-old Emily Keyes, shown in a yearbook photo as a smiling blonde who played volleyball and was on the debate team at the high school. She was pronounced dead at a Denver hospital hours after the standoff.

There was no known link between Keyes and the gunman, or between the gunman and the community. Wegener, who had a son in the school as the drama unfolded, was at a loss to explain a motive.

"We are a community in mourning," schools superintendent Jim Walpole said. "Our thoughts, our prayers are with our students, staff and their families. Especially the family of the student we lost."

"It's a big shock. We're a small community. We didn't expect it to happen to us. We're just kind of awestruck," Bellomy told FOX News.

Wegener added: "This is something that has changed my school, changed my community. My small county's gone."

Residents gathered quietly Thursday morning at the Cutthroat Cafe, where Keyes had been a waitress for about two years, to grieve and remember, said Bobbi Sterling, a waitress and cook there.

"It's very sad here. You know, the family lost their daughter but as a community, we lost a child," she said. "We're just sitting here, numb and in shock. We're all just kind of stunned. People are here for mutual support."

School was canceled for the rest of the week at the high school and the adjoining middle school.

The sheriff, a 36-year resident of Bailey, said he knew the slain girl's family and was "scared to death" as he handled the hostage situation. He said the gunman threatened the girls almost throughout the four-hour ordeal and at one point fired a shot inside the classroom.

"I have to go and eventually I have to face a family about the fact that their daughter is dead," Wegener quietly told reporters. "So, what would you do?"

The lines of students fleeing the high school and middle school, the bomb squads and the frantic parents scrambling to find their loved ones evoked memories of the 1999 Columbine High School attack, where two students killed 13 people before taking their own lives.

Michael Owens, who has one son at the middle school and another in the high school, said the anxiety was worse because the memory of Columbine was still fresh.

"Things that are out of your control, you just do what you can do," he said. "It's like an earthquake."

The situation unfolded in a narrow, winding canyon carved by the South Platte River about 35 miles southwest of Denver. Ambulances were parked in the end zone of the football field and a tank-like SWAT team vehicle was parked nearby on a closed-down highway swamped with gun-toting sheriff's officers and police.

Bill Twyford said he received a text message from his 15-year-old son Billy, a student at the high school, at about 11:30 a.m. It said: "Hey there, there's a gun hijacking in school right now. I'm fine, bad situation though."

Jessica Montgomery, 15, said she saw the suspect in a second-floor hallway shortly before noon. She described him as "creepy," with acne and stubble on his face. He motioned her to come over.

"I was like, 'the bell just rang,'" she said. "I was like, 'Why isn't he going to class?' And then I was like, 'He's kind of old.'"

Sophomore Zack Barnes, 16, said his class moved to a room that turned out to be next to the one where the hostages were being held. They turned out the lights and sat in silence in the dark for about 20 minutes before police guided them out.

"I was just praying it wasn't a mass killing," Barnes said.

The two schools have an enrollment of about 770 students, with 460 in the high school. Students from both were taken by bus to another school for a head count, and there were cheers from parents as their loved ones arrived.

FOX News' Carol McKinley and The Associated Press contributed to this report.

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