Aug. 15, 2012 -- A gunman opened fire on a security guard at the Washington D.C., headquarters of a conservative Christian organization only to be tackled and subdued by the guard whom he had just shot in the arm, authorities said.

The suspect, identified by law enforcement sources as Floyd Corkins of Herndon, Va., is alleged to have entered the offices of The Family Research Council and yelled at the guard about the organization's policies.

The shooter soon fired a handgun at the guard at around 10:50 a.m. ET.

Corkins, who himself was not shot, was subdued by the injured guard and others, officials said. Police arrested him and authorities said he was being interviewed by the FBI.

Corkins was a volunteer at the DC Center for the LGBT Community, a community center in Washington for lesbian, gay, bisexual and transgender people, where the Associated Press reported the 28-year-old often worked at the front desk.

"I was shocked to hear that someone who has volunteered with the DC Center could be the cause of such a tragic act of violence," the center's executive director, David Mariner, said in a statement released to ABC News. "No matter the circumstances, we condemn such violence in the strongest terms possible. We hope for a full and speedy recovery for the victim and our thoughts are with him and his family."

The security guard, identified by the AP as Leo Johnson, was taken to a nearby hospital.

"The security guard here is a hero, as far as I'm concerned," said Metro Police Department Chief Cathy Lanier. "He did his job. The person never made it past the front."

Later in the afternoon, authorities widened the security perimeter around the building when a suspicious package was discovered. They were also searching the suspect's car and home in Virginia.

Charges likely will be filed Thursday by the U.S. Attorney's office in Washington, sources said.

Law enforcement sources did not officially identify the suspect except to say he was from Virginia.

"We don't know enough about him or his circumstances," said James McJunkin, assistant director in charge of the FBI's Washington field office. "We are going to try to sort this all out, pull the evidence and do all the interviews we can."

Family Research Council President Tony Perkins issued a statement on the organization's website.

"The police are investigating this incident," Perkins said. "Our first concern is with our colleague who was shot today. Our concern is for him and his family."

The Family Research Council was founded in 1983 by James Dobson. Today, Perkins heads the organization, which is vocal lobbying group for conservative Christian social issues, including opposition to abortion and gay marriage.

Perkins supported Chick-fil-A President Dan Cathy, whose company has publicly taken a position against gay marriage.

"Chick-fil-A is a Bible-based, Christian-based business who treats their employees well. They have been attacked in the past about their stand. But they refuse to budge on this matter, and I commend them for what they are doing," he said.

The suspect was carrying items from a Chick-fil-A restaurant, law enforcement sources said.

President Obama was notified today at 1:18 p.m. ET of the shooting at the Family Research Council's offices in D.C. by Homeland Security Advisor John Brennan. The president expressed his concern for the individual involved in the shooting and said this type of violence has no place in our society, White House Press Secretary Jay Carney told the press pool traveling in the president's motorcade today.

ABC News' Jack Cloherty, Mary Bruce and Michael S. James contributed to this report.