As a motive remains under investigation in the fatal sniper-type shooting at a Dallas Immigration and Customs Enforcement (ICE) field office this week, law enforcement experts said the incident is part of a frightening trend of rifle-wielding shooters targeting politicians, police and others from long distances.

Homeland Security officials have also said that ICE agents are facing a “1000% increase” in assaults, though the agency has not provided data to support

A shooting at the Dallas Immigration and Customs Enforcement field office on Wednesday left one detainee dead and two others wounded, officials said. The gunman, who fired from an adjacent rooftop, died of a self-inflicted gunshot wound.

President Donald Trump promised more ICE operations after a shooting at a Dallas ICE facility killed one detainee and injured two others. Trump didn’t mention the victims in his social media post.

A Mexican national remained in grave condition after being shot at least four times in an attack earlier this week on a Dallas ICE office, his brother told a Spanish-language television network. Miguel Ángel García Medina was shot in his flank,