Watch James Comey, director of the Federal Bureau of Investigation, describe the Orlando investigation.

The suspect in the mass shooting at a gay nightclub in Orlando, Florida, appeared to have acted alone and was radicalized, said FBI Director James Comey at a briefing at FBI headquarters in Washington, D.C., on Monday.

It was not clear which terrorist organization the suspect, Omar Mateen, aligned himself or if he had contact with fighters located abroad, Comey said.

The FBI interviewed the suspect twice over incendiary comments he made to coworkers, which he said he made in anger because he thought he was being discriminated against for being a Muslim. The investigation into Mateen was closed after that.

The investigation into the mass shooting will continue, along with determining whether the agency should have done anything differently, or whether it should make any changes going forward. “We are looking for needles in a nationwide haystack,” said Comey.

“We know that this killing is upsetting to all Americans. … We hope you will channel this sense of anxiety into awareness.”