WASHINGTON — A gay rights activist was formally charged Wednesday with shooting and trying to kill a security guard at the Washington headquarters of a Christian lobby group, justice officials said in a statement.

Floyd Lee Corkins II, 28, was indicted by a grand jury on federal and Washington (District of Columbia) charges relating to the shooting last week at the Family Research Council, said the US Attorney's office in the capital.

If Corkins, of Herndon, Virginia, is convicted he faces a hefty prison sentence for allegedly wounding Leonardo Johnson in the arm.

Local Washington authorities have charged Corkins with "assault with intent to kill while armed," which is punishable by a minimum of five and a maximum of 30 years in prison.

Corkins, who has been in custody since the August 15 incident and is due back in court Friday, is also charged with "possession of a firearm during a crime of violence," which carries minimum jail time of five years and a maximum sentence of 15 years.

In a third charge, Corkins is accused of the federal crime of transporting a firearm and ammunition across state borders -- punishable by up to 10 years.

The accused is a former volunteer with Washington-based gay advocacy group The DC Center for the LGBT (Lesbian, Gay, Bisexual and Transgender) Community.

The center shut its doors in the days after the attack, issuing several statements condemning the act of violence.