DALLAS (AP) — A shooter with a rifle opened fire from a nearby roof onto a U.S. Immigration and Customs Enforcement location in Dallas on September 24, killing at least one person and wounding others before taking his own life, authorities said.

The exact motivation of the attack was not immediately known. The FBI said at a morning news conference that ammunition found at the scene contained anti-ICE messaging. The head of the agency, Kash Patel, released a photo on social media that shows a bullet containing the words “ANTI-ICE” written in what appears to be marker.

Dallas Police Chief Daniel Comeaux told reporters that officers responded to a report of four people shot, with two dead. Authorities initially said three people, including the shooter, had been shot.

Homeland Security spokesperson Tricia McLaughlin told Fox News that no ICE agents were injured.

“We believe he was shooting at law enforcement and detainees from an apartment building,” McLaughlin said. “Detainees were among the victims of the shooting.”

The FBI said during the news conference that it was investigating the shooting as “an act of targeted violence.”

The attack is the latest public, targeted killing in the U.S. and comes two weeks after conservative leader Charlie Kirk was killed by a rifle-wielding shooter on a roof.

Officers responded to a call to assist an officer at 8101 N. Stemmons Fwy. around 6:40 am Wednesday and determined that someone opened fire at a government building from an adjacent building, Dallas police spokesperson Officer Jonathen E. Maner said in an email.

The Dallas Fire-Rescue Department was also dispatched after a call reporting a shooting at or near the immigration office, department spokesperson Jason L. Evans said in an email.

Parkland Hospital received two patients from the shooting, hospital spokesperson April Foran said by telephone. She did not have any details about their conditions.

A third person died at the scene after the shooting, Maner said.

Dozens of emergency vehicles were seen along a highway near the facility.

The ICE facility is along Interstate 35 East, just southwest of Dallas Love Field, a large commercial airport serving the Dallas-Fort Worth metropolitan area, and just blocks from hotels catering to airport travelers.

Traffic cameras near the scene showed six lanes of a normally busy freeway empty, with cars and semitrailers ground to a halt on an interstate exit.

Homeland Security Secretary Kristi Noem said details were still emerging, but the agency was confirming there were “multiple injuries and fatalities” at the field office. Noem said the motive remained unclear, but noted there has been an uptick in targeting of ICE agents.

ICE and Homeland Security didn’t immediately provide additional details.

A July 4 attack at a Texas immigration detention center injured a police officer, who was shot in the neck. Attackers dressed in black military-style clothing opened fire outside the Prairieland Detention Center in Alvarado, southwest of Dallas, federal prosecutors said. At least 11 people have been charged in connection with the attack.

A man with an assault rifle fired dozens of rounds at federal agents as they were leaving a U.S. Border Patrol facility in McAllen on July 7. The man, identified as Ryan Louis Mosqueda, injured a police officer who responded to the scene before authorities shot and killed him. Police later found other weaponry, ammunition and backpacks inside his car.