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WASHINGTON(CNN) -- Police are investigating what prompted a man to walk in to the lobby of a conservative policy organization on Wednesday morning and open fire, wounding a security guard.

The guard, who was shot in the arm, helped wrestle the gunman to the ground, police said. The guard was reported to be in stable condition.

A law enforcement official said the gunman, described as a man in his late 20s, made some remarks about the Family Research Council before opening fire. He is now in custody, but has not been formally charged, the FBI said.

The shooting occurred about 10:45 a.m. in the lobby of the headquarters of the council, a Christian group that has pushed family and anti-abortion issues and religious liberties. It has been a leading opponent of same-sex 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.

DC Police Chief Cathy Lanier said the man entered the building in downtown Washington and was "confronted by a security guard."

The suspect opened firing, 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.

Law enforcement officials are interviewing the guard and others.

The FBI's Jacqueline Maguire said the case is being worked jointly by the FBI and the Metropolitan Police Department "to determine motive/intent and whether a hate crime/terrorism nexus exists."

Family Research Council President Tony Perkins said "our first concern is with our colleague who was shot today. Our concern is for him and his family."

Launched in 1983, the Family Research Council says it promotes "faith, family and freedom in public policy and public opinion."

Presumptive Republican presidential nominee Mitt Romney said he was appalled by the incident.

"There is no place for such violence in our society," he said in a statement. "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."

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