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An FBI affidavit in the investigation of a shooting Wednesday at the downtown Washington, D.C., offices of the Family Research Council says the accused gunman uttered a statement to the effect of, "I don't like your politics," before reaching into a backpack for a handgun and opening fire.

Floyd Lee Corkins II, of Herndon, Va., 28, is charged with assault with intent to kill, in addition to federal firearms charges.

Corkins was wearing a white prison jumpsuit and showed no visible emotions or reactions at federal court Thursday.

When the judge asked if the 28-year-old could afford a private attorney, Corkins responded that he only had $300 to his name. The judge assigned a public defender.

He was ordered to be held without bond and a detention hearing was scheduled for next Friday. Prosecutors also asked for a mental evaluation.

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Leo Johnson, an unarmed building operations manager, is being lauded by D.C. police as a hero for stopping and disarming Corkins before he could get into the building.

Surveillance video shows Johnson interacting with Corkins before he allegedly opened fire, striking Johnson in the arm. The security guard managed to wrestle Corkins to the ground and disarm him before he could get inside the group's offices.

"The security guard here is a hero, as far as I¹m concerned," D.C. Police Chief Cathy Lanier said. "He did his job. The person never made it past the front."

Sources told Fox News that after Johnson disarmed Corkins, the gunman said: "Don't shoot me, it was not about you, it was what this place stands for."

Johnson underwent surgery late Wednesday. Tony Perkins, president of the Family Research Council, visited the hospital and said the surgery "went well" in a statement to Fox News.

"When I told him his actions were heroic in protecting his colleagues, he told me that he just reacted in the way he thought anyone at FRC would have responded," Perkins' statement read. "We are very grateful for the outpouring of prayers from literally around the world."

Perkins gave his first interview to Fox News' "America Live." He made it clear that he blamed the suspect for the shooting, but said he was "given a license" by groups like the Southern Poverty Law Center, which labeled the Family Research Council as a hate group.

"I think it's time for people to realize what the Southern Poverty Law Center is doing with their reckless labeling of organizations that they disagree with," he said.

The Southern Poverty Law Center declined an interview request from the program.

Corkins had volunteered recently at a community center for lesbian, gay, bisexual and transgender people. Two law enforcement officials said Corkins was carrying sandwiches from Chick-fil-A, a fast-food chain whose chief executive¹s public opposition to same-sex marriage led to a heated national cultural debate, including boycotts and events held in support of the Atlanta-based chain.

Authorities say Corkins was carrying a 9-mm. Sig Sauer handgun that was purchased and owned legally, said Richard Marianos, special agent in charge of the federal Bureau of Alcohol, Tobacco, Firearms and Explosives' Washington field office.

Corkins' backpack contained 50 rounds of ammunition and 15 Chick-fil-A sandwiches, the FBI affidavit said.

The accused gunman's parents also told the FBI that their son held "strong opinions with respect to those who do not treat homosexuals in a fair manner," the affidvit said.

Authorities were investigating the attack as a case of domestic terrorism, although James McJunkin, the head of the FBI¹s Washington Field Office, said authorities do not yet know the gunman's motive.

"We don't know enough about him or his circumstances to determine what his connection is to this group [the research council] or his mental state, or what he was doing or thinking of doing," McJunkin said Wednesday. "So we're going to try to sort this all out, pull the evidence together, do all the interviews we can."

Corkins had been volunteering for roughly six months at The DC Center for the LGBT Community, according to David Mariner, executive director of the northwest Washington community center. Corkins usually staffed the center's front desk on Saturdays, and his most recent shift was about two weeks ago.

"He always struck me as a kind, gentle and unassuming young man," Mariner said. "I'm very surprised that he could be involved in something like this."

Mariner said he did not know Corkins well or have any conversations with him about the Chick-fil-A controversy or other political issues of interest to the gay community.

"I really only talked to him about volunteering, so I couldn't say anything about anything else," Mariner said.

The Family Research Council, according to its website, is a conservative nonprofit organization that seeks to advance "faith, family and freedom in public policy and public opinion." The group strongly opposes gay marriage and abortion and maintains a powerful lobbying presence on those causes, often testifying before Congress. The organization had also defended Chick-fil-A President Dan Cathy for his remarks opposing gay marriage.

Meanwhile, advocacy groups across the ideological spectrum condemned the violence, with some casting it as a hate crime.

"Today's attack is the clearest sign we've seen that labeling pro-marriage groups as `hateful' must end," Brian Brown, the president of the National Organization for Marriage, said in a statement.

White House spokesman Jay Carney said President Obama, who was traveling in Iowa Wednesday, was informed of the 10:45 a.m. shooting shortly after 1 p.m.

"The president expressed his concern for the individual injured in the shooting and his strong belief that this type of violence has no place in our society," Carney said.

Republican presidential candidate Mitt Romney said in a statement that he was appalled.

"There is no place for such violence in our society," he said. "My prayers go out to the wounded security guard and his family, as well as all the people at the Family Research Council whose sense of security has been shattered by today's horrific events."

Authorities later seized Corkins' car at a northern Virginia Metro station and interviewed neighbors, several of whom spoke highly of his family.

"They were always so sweet and so nice," said Stephanie Meyer, who lives nearby Corkins' Virginia home. "They are awesome people. We never had any issues."

Corkins is not a member of the Air Force, but he may have lived at Andrews Air Force Base in some other capacity in the past, possibly as a dependent or family member, according to a U.S. Defense Department official who spoke on condition of anonymity because the official was not authorized to provide personal information.

Amy Biondi and her husband Steve were visiting Washington from Long Island with their daughter and a friend and tried to ask officers for help with a parking meter when they were told there was a situation they had to deal with. The door to the FRC was opened, and an officer could be heard repeatedly shouting, "Put the gun down, put the gun down."

"Next thing you know there are police officers swarming the area," said Biondi, 45, a massage therapist from St. James, N.Y.

The family didn't get a close look inside, but they said the man that officers were talking to seemed to comply immediately.

Fox News' Mike Levine and The Associated Press contributed to this report.