A gunman scrawled anti-ICE messages on the bullets used to kill a migrant detainee in an attack on a Dallas immigration centre, officials said.

The sniper struck three people, killing one and injuring two others, before killing themself at the Immigration and Customs Enforcement (ICE) facility in Dallas, Texas, on Wednesday morning.

Kash Patel, the FBI director, said the attack was ideological and shared an image of an unused round found at the scene with “anti-ICE” written on it.

“These despicable, politically motivated attacks against law enforcement are not a one-off,” he said.