A 28-year-old Virginia man was held late Wednesday on a charge of assault with a deadly weapon after a security guard was wounded in the lobby of the Family Research Council, a conservative policy organization, authorities said.
Police and federal agents were investigating what prompted the suspect, identified by the FBI as Floyd Lee Corkins II, to walk into the group's headquarters about 10:45 a.m. and open fire.
Corkins, is from Herndon, a suburb of Washington, the FBI said in a statement about the charge.
The guard helped wrestle the gunman to the ground. Called a hero by police, the security officer was in stable condition after being shot in the arm.
A law enforcement official said the gunman made some remarks opposing the Family Research Council's policies before opening fire.
A source working with the DC Center for the LGBT Community told CNN that Corkins had worked as a volunteer at the center.
David Mariner, executive director of that center, released a statement Wednesday night saying he was "shocked to hear that someone who has volunteered with the DC Center could be the cause of such a tragic act of violence.
"No matter the circumstances, we condemn such violence in the strongest terms possible. We hope for a full and speedy recovery for the victim and our thoughts are with him and his family," Mariner said in the statement.
A backpack and a vehicle believed to belong to the suspect were recovered, the law enforcement official told CNN.
The suspect's weapon was a legally obtained 9mm handgun, according to another law enforcement official. The suspect had obtained the weapon "fairly recently" from a gun shop in Virginia.
The council is a Christian group that has pushed family and anti-abortion issues and religious liberties. It has been a leading opponent of same-sex marriage.
The Family Research Council recently backed restaurant chain Chick-fil-A after the company's president, Dan Cathy, said the company supports traditional marriage.
Investigators said that it was too early to say whether the organization was targeted for its political views, but made clear that would be part of the investigation.
"We don't know enough yet about him or his circumstances to be able to determine his connection to this group or to the business or to what, you know, mentally what he's doing or thinking. So we're going to try to sort it all out, and pull the evidence together, do as many interviews as we can, and get it all together," said FBI Assistant Director James McJunkin.
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DC Police Chief Cathy Lanier said the man entered the building in downtown Washington and was "confronted by a security guard."
The suspect opened fire, striking the guard.
"The security officer here is a hero as far as I'm concerned. He did his job. The person never made it past, farther then the front door," Lanier said.
Steve Biondi, a tourist from New York, said he witnessed the first two police officers arrive at the scene. They ordered the suspect to put the gun down. The man got on the ground, and did not appear to put up a fight, according to Biondi.
He described the suspect as about 6 feet tall and weighing about 240 pounds.