A gay rights worker is being held by police after the shooting of a security guard at the offices of the Family Research Council (FRC), a pro-family, pro-religion think tank in Washington D.C.

The attack has been condemned by President Barack Obama and Republican party presidential candidate, Mitt Romney.

Brian Brown, the President of the National Organisation for Marriage said that the shooting was “the clearest sign we’ve seen that labeling pro-marriage groups as ‘hateful’ must end”.

The suspect, who has been named as Floyd Corkins,had been volunteering at The DC Centre for the LGBT Community for the past six months or so, according to David Mariner, the executive director of the centre.

Corkins, 28, of Herndon, Virginia, entered the lobby of FRC yesterday morning, where witnesses say he criticised the organisation, which is opposed to same-sex marriage, before opening fire. One security officer was shot in the arm before the officer was able to subdue Corkins with the assistance of others.

Sources told Fox News that after the guard took away his gun, the suspect said, “Don’t shoot me, it was not about you, it was what this place stands for.”

Corkins was reportedly armed with multiple weapons.  

The guard, Leo Johnson, was shot in the arm and was conscious after the shooting and in stable condition. The FBI are believed to be questioning the suspect.  

The suspect “made statements regarding their policies, and then opened fire with a gun striking a security guard,” a source told Fox News.

Authorities were treating the attack as a case of domestic terrorism, although James McJunkin, the head of the FBI’s Washington Field Office, said authorities do not yet know the gunman’s motive.

“We don’t know enough about him or his circumstances to determine what his connection is to this group [the research council] or his mental state, or what he was doing or thinking of doing,” McJunkin said. “So we’re going to try to sort this all out, pull the evidence together, do all the interviews we can.”

President Obama condemned the shooting, with his spokesman, Jay Carney, telling the press that Obama expressed his concern for the victim and said that such violence has no place in society.

Brian Brown of Nom commented: “The Southern Poverty Law Centre (a U.S. liberal group) has labeled the Family Research Council a ‘hate group’ for its pro-marriage views, and less than a day ago the Human Rights Campaign issued a statement calling FRC a ‘hate group’—they even specified that FRC hosts events in Washington, DC, where today’s attack took place.

“NOM has always condemned all violence and vilification connected to our ongoing national debate about the meaning and definition of marriage. For too long national gay rights groups have intentionally marginalised and ostracised pro-marriage groups and individuals by labeling them as ‘hateful’ and ‘bigoted’ — such harmful and dangerous labels deserve no place in our civil society.”

Meanwhile, 23 organizations supporting gay rights have condemned the shooting saying that although the motive of the attack hasn’t been clearly established, the leaders “utterly reject and condemn” such violence.

“We were saddened to hear news of the shooting this morning at the offices of the Family Research Council. Our hearts go out to the shooting victim, his family, and his co-workers,” said the leaders in a statement.

The statement from LGBT rights leaders said that, “The motivation and circumstances behind today’s tragedy are still unknown, but regardless of what emerges as the reason for this shooting, we utterly reject and condemn such violence.

“We wish for a swift and complete recovery for the victim of this terrible incident.”