Notes written by the person suspected of opening fire on an immigration facility in Texas indicate he was targeting ICE agents and did not intend to harm detainees, acting US attorney for the Northern district of Texas Nancy Larson said.
One detainee was killed and two others critically injured after a suspected sniper opened fire at an Immigration and Customs Enforcement (ICE) centre in Dallas on Wednesday, officials said.
Speaking at a news conference on Thursday, Ms Larson identified the shooter as 29-year-old Joshua Jahn, adding notes he had written had been found at his home.
She said he intended to maximize lethality against ICE personnel and to maximize property damage at the facility.
He hoped to minimize any collateral damage or injury to the detainees and any other innocent people, she added. It is clear from these notes that he was targeting ICE agents and ICE personnel.
The victims have not yet been identified.
FBI director Kash Patel noted that evidence so far suggests a high degree of pre-attack planning. One of the handwritten notes found stated: Hopefully this will give ICE agents real terror, to think, 'is there a sniper with AP rounds on that roof?'
Larson confirmed that the shooter very likely acted alone during his assault that targeted the length of the building with gunfire.
The notes contained a gameplan of the attack emphasizing the shooter's intention to terrorize ICE employees and interfere with their work.
No evidence was found linking him to any specific group; however, he expressed his hatred for the federal government.
The bravery of ICE and other federal agents was praised, as they worked under fire to evacuate detainees to safety.
FBI special agent Joe Rothrock described the situation as a targeted, ambush-style attack on law enforcement aiming specifically to kill ICE agents.
Marcos Charles, an ICE field office director, echoed the sentiment of halting violent rhetoric against the agency: In contrast to those who would demonize our men and women, yesterday our brave officers ran back into danger.