A shooter killed at least one person and wounded others in a shooting on Wednesday at an Immigration and Customs Enforcement field office in Dallas before dying of a self-inflicted gunshot wound, local and federal authorities said.

Police responded to reports of the shooting at the office in northwest Dallas at about 6:40 a.m. local time (1140 GMT), the Dallas police department said on X.

The suspect opened fire on the office from an adjacent building, according to the preliminary investigation, police said. Two people were transported to a hospital with gunshot wounds, while a third person died at the scene.

ICE officers were not injured, but it was not clear whether the victims included ICE detainees, local security or local law enforcement, Department of Homeland Security spokeswoman Tricia McLaughlin said in an interview on Fox News' "Fox & Friends."

Investigators are looking at the possibility the shot came from the rooftop of a nearby apartment building, McLaughlin said.

"Those details are still murky. It looked like it might have been a sniper or some sort of a long-form shot,” McLaughlin said.

She also said the shooting took place at an ICE field office, not a detention facility, where ICE officers conduct short-term processing of recently-arrested detainees.

The victims were being led into the building to be processed and repatriated, Fox News reported, citing Dallas police department sources.

Local news footage showed heavy law enforcement response around the facility.

The shooter was found dead on the roof of a nearby building, local ABC affiliate WFAA reported, citing sources.

"Preliminary information is a possible sniper," ICE acting Director Todd Lyons told CNN.

Police were expected to hold a news briefing later in the morning.