A gunman who wrote "ANTI-ICE" on an unused bullet killed one detainee and wounded two others on Wednesday when he fired on an Immigration and Customs Enforcement field office in Dallas from a nearby rooftop before taking his own life, officials said.

FBI Director Kash Patel posted a photo on X of what he said was the suspect's unused ammunition, showing the shell casing of one round inscribed with the phrase "ANTI-ICE" along the side.

"While the investigation is ongoing, an initial review of the evidence shows an ideological motive behind this attack," Patel wrote.