DALLAS, USA: The gunman who opened fire on an Immigration and Customs Enforcement field office in Dallas left behind a collection of notes at his home saying he acted alone in an attack that was intended to terrorize ICE agents and minimize harm to detainees at the facility, officials said on Thursday.

Nancy Larson, acting US attorney for the northern district of Texas, said at a news conference that the shooter’s writings were discovered during a search of his home in Fairview, Texas, following Wednesday’s pre-dawn shooting.

Earlier in the day, FBI Director Kash Patel said the suspect had searched for apps in August that track the location of ICE agents and downloaded a list of local Department of Homeland Security facilities.

Patel also said in a social media post that investigators determined that the suspect had researched video of conservative activist Charlie Kirk’s highly publicized assassination before carrying out Wednesday’s pre-dawn attack in Texas.

One immigration detainee at the Dallas site was shot dead and two others were critically wounded. No federal personnel were injured in the incident.