Federal officials say the Dallas shooter, identified as Joshua Jahn, specifically targeted U.S. Immigration and Customs Enforcement (ICE) agents.

Notes found at his residence showed hatred toward ICE and revealed that he had planned the attack in advance.

Jahn used a ladder to climb onto a nearby rooftop early Wednesday morning, where he opened fire with a legally purchased 8mm bolt-action rifle.

Three detainees inside a van were hit, with one killed and two critically injured, while law enforcement risked their lives to move others to safety.

Authorities said Jahn acted alone, citing another note in which he wrote, “Yes, it was just me.” He was later found dead of a self-inflicted gunshot wound by Dallas police officers, CBS News has reported.

ICE officials blamed “wild rhetoric” and the use of tracking apps for fueling attacks on ICE agents, which they say have surged by 1,000%.