DHS said the shooter “fired indiscriminately at the ICE building, including at a van in the sallyport where the victims were shot”.
Two detainees were killed and a third is in critical condition, it said.
The ICE facility, which came under attack, processes detainees before they are transferred to a long-term detention centre, according to US media reports.
Homeland Security Secretary Kristi Noem and Vice-President JD Vance condemned rhetoric directed at ICE since Trump’s return to office.
“For months, we’ve been warning politicians and the media to tone down their rhetoric about ICE law enforcement before someone was killed,” Noem said on X. “These horrendous killings must serve as a wake-up call to the far-left that their rhetoric about ICE has consequences.”
Other recent attacks
“The obsessive attack on law enforcement, particularly ICE, must stop,” Vance said on the social media platform.
ICE’s prominent role in the Trump immigration crackdown has sparked widespread criticism over its use of armed, masked agents to conduct raids in public places against undocumented migrants.
After ICE immigration raids in Los Angeles spurred unrest and protests earlier this year, Trump dispatched the National Guard and US Marines to the California city.
Another ICE facility in Texas was the target of an attack in July that left a police officer wounded in the neck.
Ten people have been charged for their roles in the attack on the ICE centre in the town of Alvarado.
According to a criminal complaint, the assailants, dressed in black military-style clothing, shot fireworks at the ICE facility and spray-painted “Traitor” and “ICE Pig” on cars and a guard structure.
The Alvarado incident came just days before a man armed with an assault rifle opened fire at a US Border Patrol facility in McAllen, Texas.
The 27-year-old man fired dozens of rounds from an assault rifle at the entrance of the Border Patrol annex before being shot dead.
Two police officers and a Border Patrol employee were injured.
– Agence France-Presse