An affidavit made public Thursday says Corkins walked into the FRC offices at 11 a.m. EDT Wednesday and shot security guard Leonardo Reno Johnson. Corkins was charged in U.S. District Court in Washington with assault with intent to kill while armed and interstate transportation of a firearm and ammunition, The Washington Post reported.
He was ordered held without bond and scheduled to appear at a hearing Aug. 24. Corkins could get up to 30 years in prison for the assault charge, the newspaper said.
Corkins pulled a 9mm handgun from his bag and said, "I don't like your politics," before shooting Johnson in the arm, the affidavit states. Johnson was able to take the gun from Corkins and restrain him.
Corkins had worked as a volunteer at a Washington organization that provides services and support to lesbian, gay, bisexual and transgender people.
"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," FBI Assistant Director James McJunkin said.
David Mariner, executive director of the LGBT center, said in a statement that "no matter the circumstances, we condemn such violence in the strongest terms possible."
The Southern Poverty Law Center, which tracks hate groups, has listed the FRC as a hate group since 2010.
FRC President Tony Perkins told Fox News Thursday he blames the SPLC for the shooting.
"I think it's time for people to realize what the Southern Poverty Law Center is doing with their reckless labeling of organizations that they disagree with," he said.
Mark Potok, senior fellow at SPLC, said Thursday the organization "deplores all violence" and called Perkins' accusation "outrageous."
"For more than 40 years, the SPLC has battled against political extremism and political violence," Potok said in a statement. "We have argued consistently that violence is no answer to problems in a democratic society, and we have strongly criticized all those who endorse such violence, whether on the political left or the political right."
Potok said the FRC was designated as a hate group "because it has knowingly spread false and denigrating propaganda about LGBT people -- not, as some claim, because it opposes same-sex marriage."
"Perkins and his allies, seeing an opportunity to score points, are using the attack on their offices to pose a false equivalency between the SPLC's criticisms of the FRC and the FRC's criticisms of LGBT people," Potok said.