The 28-year-old Herndon man accused of shooting a security guard at the Family Research Council last summer pleaded guilty to multiple charges Wednesday, accepting responsibility for his plan to kill as many people as he could at the conservative lobbying organization's headquarters.

Floyd Corkins II pleaded guilty to a federal firearms charge and D.C. terrorism and assault charges.

On the morning of Aug. 15, 2012, Corkins entered the office of the FRC, located 801 G St. NW. Corkins encountered unarmed security guardLeo Johnson,took a 9mm handgun from his backpack and shot Johnson in the arm, prosecutors said. After Johnson was injured, he wrestled the weapon away from Corkins and subdued him.

Police officers frisked Corkins and found two loaded magazine clips and a list that mentioned the FRC and three other organizations that oppose gay marriage. Police also found15 Chick-fil-A sandwiches and 50 more rounds of ammunition in Corkins' backpack. Not long before the incident, a senior Chick-fil-A executive had made headlines for his public opposition to same-sex marriage.

When Corkins was interviewed by FBI agents, he acknowledged that he went to the FRC to kill people and smear Chick-fil-A sandwiches in his victims' faces, prosecutors said. Corkins said that he wanted to do this "to make a statement against the people who work in that building ... and with their stance against gay rights," according to a court document.

Corkins told the agents that he identified the FRC as an anti-gay organization on the website for the Southern Poverty Law Center, a civil rights organization. In a statement released Wednesday, FRC President Tony Perkins asked the SPLC to stop labeling anti-gay organizations as hate groups.

"The Southern Poverty Law Center can no longer say that it is not a source for those bent on committing acts of violence," Perkins said. The SPLC has defended its decision to label the FRC as a hate group, arguing that the FRC "has knowingly spread false and denigrating propaganda about LGBT people."

Corkins is scheduled to be sentenced on April 29. The terrorism and assault offenses each carry maximum penalties of 30 years in prison, and the weapons-related charge has a maximum penalty of 10 years in prison.