The man accused of opening fire at a Dallas Immigration and Customs Enforcement field office on Wednesday, killing one detainee and wounding two others, has been identified as 29-year-old Joshua Jahn, according to officials.
Jahn, a U.S. citizen from Fairview, Texas, died from a self-inflicted gunshot wound, authorities said.
He "very likely" acted alone and "indicated he did not expect to survive the attack," officials said during a press conference on Thursday.
Here's what we know about the suspect.
Jahn used an 8 mm bolt-action rifle in the shooting, officials said during a press conference on Thursday.
The suspect had purchased the weapon legally in August, according to Joe Rothrock, the special agent in charge of the Dallas FBI field office.
FBI Director Kash Patel posted that Jahn allegedly left a handwritten note that read, "Hopefully this will give ICE agents real terror, to think, 'is there a sniper with AP rounds on that roof?" -- referring to armor-piercing bullets.
FBI officials previously said rounds found near the suspect contained "messages that are anti-ICE in nature."
Patel released an image of recovered shell casings, including one that had been engraved with the phrase "ANTI ICE," he said.
Patel also said "further accumulated evidence to this point indicates a high degree of pre-attack planning," with the suspect allegedly downloading a document titled "Dallas County Office of Homeland Security & Emergency Management" that contained a "list of DHS facilities."
Jahn also allegedly "searched apps that tracked the presence of ICE agents," Patel said. He added the suspect "conducted multiple searches of ballistics and the 'Charlie Kirk Shot Video'" between Sept. 23 and Sept. 24.
Nancy E. Larson, acting U.S. attorney for the Northern District of Texas, revealed more details on the suspect's notes during the press conference on Thursday, including that he had a "game plan of the attack" and that he hoped the attack would give ICE agents "real terror."
"What he did is the very definition of terrorism," Larson said.
Larson also said Jahn "hoped to minimize collateral damage to detainees" and wanted to "cause terror" to ICE employees.
Officials said Jahn's notes included "no specific government agency other than ICE,", with Jahn calling the work of ICE agents "human trafficking."
Larson also revealed the suspect left a handwritten note that said, "Yes, it was just me and my brain," which indicated to investigators that he acted alone in the shooting.
Officials are not aware of Jahn having a membership in any specific group or entity.
A spokesperson for the University of Texas – Dallas said that a person matching Jahn’s name and date of birth had "briefly attended" the university "over a decade ago."
Two childhood friends told ABC News they had not seen Jahn in around 10 years, but remembered him as mainly interested in video games and internet culture.
Both friends asked not to be named due to concerns about potential harassment.
"This is a complete shock to me," one of the friends told ABC News. "Josh was the least political out of all the people I knew in high school. He liked playing video games."
Both friends provided a username that they said belonged to Jahn on the gaming website Steam, which is also linked to a Reddit account.
The Reddit account has not been used in around six years. Previous posts point to an interest in gaming and smoking marijuana.
In addition to the Reddit account, the Steam profile appearing to belong to Jahn pointed to the life of an avid gamer, with over 10,000 hours spent playing games like Team Fortress 2, Left 4 Dead 2, and Rust.