The suspected gunman in an attack on a U.S. Immigration and Customs Enforcement facility in Dallas said he wanted to inflict "real terror" on agents, a federal prosecutor said Thursday.

Handwritten notes retrieved from the home of suspected shooter 29-year-old Joshua Jahn expressed "hatred for the federal government" and a desire to give ICE agents a taste of terror, Nancy Larson, acting U.S. attorney for the Northern District of Texas, said on Sept. 25.

The latest details shared by federal investigators are the firmest details yet of what inspired the shooting that left one person dead and two critically injured.

"This, what he did, is the very definition of terrorism," Larson said.

The notes described a "gameplan of the attack" and a wish to "terrorize ICE employees and interfere with their work, which he called human trafficking," said Larson, adding Jahn also wished to "minimize any collateral damage or injury to the detainees."

Instead the attack on Sept. 24 at the Dallas immigration agency field office left a detainee dead and two critically injured. Larson called the result a "tragic irony for his evil plot." No law enforcement agents were injured. Authorities say Jahn was found dead of a self-inflicted gunshot wound at the scene.

FBI officials said the gunman fired from a nearby rooftop at vehicles carrying federal agents and detainees. The gunman also fired multiple shots into the windows of the office building where immigration enforcement employees were working. The Dallas facility also serves as a processing center for detainees arrested by immigration agents.

The release of information based on the suspected shooter’s writing comes a day after the attack. Initially, the only information regarding what inspired the shooting that authorities shared came from an unspent shell casing located near Jahn’s body. The casing has the phrase "ANTI-ICE" written on it, according to FBI Director Kash Patel.

Authorities believe Jahn acted alone. Larson said Jahn claimed full responsibility for the attack, writing "Yes, it was just me and my brain." Investigators did not find evidence of "membership in any specific group or entity."

Jahn also allegedly wrote "good luck with the digital footprint," which authorities are taking to mean Jahn deleted evidence from his devices, according to Larson.

The attack is the latest shooting to stir a tense national debate over political rhetoric and acts of violence. Two weeks earlier, conservative activist and President Donald Trump ally Charlie Kirk was killed with a single shot during a speaking event at a Utah university.

As a result of the Sept. 24 shooting, ICE facilities are ramping up security, officials said.

Contributing by Christopher Cann.

This article originally appeared on USA TODAY: Dallas ICE gunman wanted to inspire 'real terror': DOJ

Reporting by Michael Loria, USA TODAY / USA TODAY

USA TODAY Network via Reuters Connect