The sniper who opened fire on the Dallas Immigration and Customs Enforcement field office, killing one detainee and wounding two detainees, was targeting ICE agents, not detainees, officials said, citing notes the suspect left behind.

The suspect — Joshua Jahn, 29, who died from a self-inflicted gunshot wound after Wednesday’s shooting — wanted to “maximize lethality against ICE personnel and maximize property damage at the facility,” Nancy E. Larson, acting U.S. attorney for the Northern District of Texas, said at a news conference on Thursday.

“It seems that he did not intend to kill the detainees or harm them. It’s clear from these notes that he was targeting ICE agents and ICE personnel,” Larson said, calling it “tragic irony” that detainees, not agents, were shot.

Evidence shows “a high degree” of planning from Jahn, of Fairview, Texas, according to FBI Director Kash Patel.

He allegedly left behind a note that said, “Hopefully this will give ICE agents real terror, to think, ‘is there a sniper with AP rounds on that roof?'” Patel said in a statement, the note referring to armor-piercing bullets.

Patel said the sniper allegedly had searches last month on apps that track ICE agents and he allegedly downloaded a document called “Dallas County Office of Homeland Security & Emergency Management,” which has a list of DHS facilities.

“He conducted multiple searches of ballistics and the ‘Charlie Kirk Shot Video'” on Tuesday and Wednesday, Patel said.

Jahn allegedly “fired indiscriminately” at the ICE building and an ICE van on Wednesday morning, killing one detainee and critically wounding two others, one of whom is a Mexican national.

Officials said they believe Jahn — armed with a bolt-action rifle legally obtained in August — brought a ladder to position himself on top of an adjacent building.

Detainees were being unloaded from a van when the gunfire erupted, officials said. The detainees in the van were being restrained for transport, per proper procedure, officials said.

“While under fire,” “heroic” officers worked to take the detainees to safety, Larson said.

Jahn’s handwritten notes indicated he did not expect to survive the shooting, officials said.

Investigators have not found that Jahn was a member of any specific group, Larson said. No government agency was mentioned in his notes other than ICE, but he did express a “hatred for the federal government,” Larson said.

Investigators believe Jahn acted alone, Larson said. She said he wrote in one note, “Yes, it was just me and my brain.”

President Donald Trump on Thursday blamed the “radical left” for the shooting.

On Wednesday, the FBI released an image of recovered bullets, including one engraved with the phrase “ANTI-ICE,” and DHS released a photo that appears to show a gunshot in an American flag display.

Acting ICE Director Todd Lyons said he would put all ICE facilities on a higher alert.