Two detainees have died and another is critically injured after a rooftop sniper opened fire at an Immigration and Customs Enforcement (ICE) centre in Dallas, Texas, officials say.

The gunman fired indiscriminately at the ICE facility and at a nearby unmarked van, law enforcement officials say, before dying from a self-inflicted gunshot wound.

No law enforcement were injured. FBI Director Kash Patel posted a photo on X of unused ammunition recovered from the scene. One casing has the phrase ANTI-ICE on it.

This incident is the latest in a string of attacks on ICE facilities in recent months as the agency ramps up efforts to deliver on US President Donald Trump's pledge for mass deportations.

While the investigation is ongoing, an initial review of the evidence shows an ideological motive behind this attack, Patel wrote, noting it as an example of politically motivated violence. He emphasized that this is not a one-off incident.

Dallas police said a preliminary investigation determined that the suspect had opened fire from an adjacent building, targeting the ICE building, included a van in the sallyport where the victims were shot, according to statements from the Department of Homeland Security (DHS).

Acting director of the Dallas ICE office Joshua Johnson stated this was the second time he faced the media regarding gun violence at his facilities, accusing divisive political rhetoric of fueling such incidents.

Texas Senator Ted Cruz echoed the sentiment, condemning politically motivated violence and urging for respectful discourse among political opponents.

Homeland Security Secretary Kristi Noem and other officials called this shooting a wake-up call regarding the consequences of extreme rhetoric against ICE.

The quarantined ICE field office had previously faced protests and threats, highlighting ongoing tensions surrounding immigration policies in the U.S.