A gunman who shot a security guard at the Family Research Council office in Washington, D.C., was carrying a handgun and several additional rounds of ammunition, federal investigators told NBC News.

Washington, D.C., police say the man, in his late 20s, walked into the headquarters of the conservative Christian lobbying group around 10:45 a.m. When challenged by the security guard, the gunman shot the guard in the arm.

He was then detained by other guards, and both district police and the FBI responded.  He was taken into custody by FBI agents. The FBI will have jurisdiction if the incident turns out to be a hate crime.

The FBI said the security guard is being treated in the hospital and "doing OK."

One law enforcement official told NBC News it's fairly clear the Family Research Council was the man's target, though the FBI has yet to specify either a motive or the target of the attack.