D.C. Police Chief Cathy Lanier

AP

A man who had been a volunteer at a community center for gays walked into the lobby of a conservative political organization, made a negative comment about what the group stands for, pulled a gun and opened fire, authorities said.

But the shooting Wednesday morning at the downtown Washington headquarters of the Family Research Council left only one person injured: the security guard. And after being struck in the arm, he helped wrestle the gunman to the floor, thwarting an attack that police fear could have turned deadly, reports The Associated Press.

"The security guard here is a hero, in my opinion," D.C. Police Chief Cathy Lanier said of Leo Johnson, who was conscious and in stable condition at an area hospital after the shooting.

Police and the FBI were investigating why the armed man, identified as 28-year-old Floyd Lee Corkins II of Herndon, Va., entered the front lobby of the conservative group, argued with the guard and opened fire. But one law enforcement official, speaking on condition of anonymity, said the suspect made a negative reference about the group's work and what it stands for before shooting.

Corkins was being held on a charge of assault with a deadly weapon, the FBI said Wednesday night. Bill Miller, a spokesman for the U.S. Attorney's Office, said Corkins would likely appear in court Thursday but gave no further details.

Television news footage showed the suspect, a large man with a shaved head and an unbuttoned striped shirt, being led to a car with his hands restrained. It was not immediately clear if he had a lawyer. Corkins was carrying a 9mm Sig Sauer handgun that authorities have determined 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.