The gunman who opened fire at a U.S. Immigration and Customs Enforcement facility in Dallas, Texas, sought “real terror” for agents and “searched apps that tracked the presence” of ICE personnel, FBI Director Kash Patel revealed Thursday.

Joshua Jahn, 29, was identified by sources familiar with the investigation as the shooter who fired from a rooftop toward the ICE facility, killing one detainee and injuring two others. The shooter died after turning the gun on himself, authorities said.

“FBI Dallas and FBI HQ have been working 24/7 to seize devices, exploit data, and process writings obtained on location and in the subject’s person/residence/bedroom,” Patel wrote on X. “One of the handwritten notes recovered read, ‘Hopefully this will give ICE agents real terror, to think, ’is there a sniper with AP [armor-piercing] rounds on that roof?'”

Patel also said that the gunman searched for videos of Charlie Kirk’s assassination in Utah leading up to the attack in Dallas on Wednesday.

Dallas police officers investigate the scene where a shooter opened fire on a U.S. Immigration and Customs Enforcement (ICE) facility on Wednesday, Sept. 24, 2025, in Dallas, Texas.  (Stewart F. House/Getty Images)

From a nearby rooftop, Jahn allegedly fired “indiscriminately” at the ICE building, as well as at a van in the sally port where the victims were shot, the DHS said.

The three detainees were in an unmarked transport van when they were shot, before Jahn took his own life around 7 a.m., according to sources. Authorities said the gunman was found dead with a rifle on a nearby rooftop. 

Law enforcement personnel respond at the scene of a shooting at an Immigration and Customs Enforcement (ICE) field office in Dallas, Texas, on Sept. 24, 2025.  (Jeffrey McWhorter/Reuters)

A photo posted on X by Patel showed what appeared to be rifle-caliber ammunition affixed to a clip. The rounds were engraved with an “anti-ICE” message, Patel said.