ATLANTA — A man charged in a string of shootings near Atlanta that left three people dead, including a Department of Homeland Security employee who was walking her dog, died in jail Tuesday night, authorities said.

Olaolukitan Adon Abel, 26, was found in his cell unresponsive, according to a statement from the DeKalb County Sheriff’s Office. Officials performed lifesaving measures on the U.S. Navy veteran, but he was later pronounced dead.

The official cause of death has not been determined, but officials don’t suspect foul play, according to the office. Officials are conducting an internal review.

Adon Abel was accused of killing Prianna Weathers, 31, and DHS auditor Lauren Bullis, 40, in last week’s attack. Authorities had also been seeking an additional murder charge for Tony Mathews, 49, who was injured in the attack and died Sunday.

Authorities haven’t offered a potential motive for the shootings. It’s unclear if Adon Abel knew any of the victims — police have said they believe at least one was targeted at random.

Adon Abel’s roommates told The Associated Press that shortly before the shootings, he got in an intense argument over the air conditioning in their home and stormed out. He lived with six others in separate units of the home.

The United Kingdom native was granted U.S. citizenship in 2022 while serving in the U.S. Navy and stationed in the San Diego area.

The attacks quickly drew the Trump administration’s attention, with Homeland Security Secretary Markwayne Mullin raising concern that Adon Abel was granted U.S. citizenship when Democrat Joe Biden was president. Mullin cataloged a litany of Adon Abel’s previous alleged crimes, but it is unclear whether any of them occurred before he became a citizen.