The man accused of murdering a 19-year-old student in the parking garage on the University of Illinois at Chicago campus allegedly became “angry” when she ignored his catcalls, authorities said.

Sophomore Ruth George was attacked after a Lyft dropped her off on campus just after 1:30 a.m. Saturday as she returned from a semi-formal event, according to a charging document for 26-year-old suspect Donald Thurman.

One of George’s friends went back to her dorm while George walked alone to the parking garage on Halsted Street, where she had parked her car, prosecutors said. As she walked past a bus stop, Thurman allegedly noticed her and “thought she was pretty and tried talking to her,” but George ignored him and continued walking.

Thurman, who was wearing a “distinctive white jacket,” was seen on surveillance video following George to where her car was parked, according to the court document. Thurman then allegedly catcalled her and tried to talk to her again, but George continued to ignore him.

When George got to her car, Thurman allegedly “was angry that he was being ignored,” the charging document states. He then allegedly grabbed her neck from behind and put her in a choke hold, causing her to fall to the ground.

While she was unconscious, Thurman allegedly threw George into the back of her car and sexually assaulted her, authorities said.

George’s family became concerned when she didn’t return home, and they went to the parking garage with police after her phone’s location pinged there. Around 11 a.m. Saturday, her sisters found her body face-down in the backseat of her car with her pants pulled down and her bodysuit ripped, prosecutors said.

Investigators found marks made from George’s shoes while she was being dragged on the scene, as well as a used condom in the car, according to the charging document.

Surveillance video allegedly showed Thurman running from the parking garage about 35 minutes after he followed George inside the structure. The white jacket he was wearing at the time was found at his home, prosecutors said.

Thurman was arrested when he returned to the area on Sunday and allegedly admitted during an interview that he choked George and threw her in the car. He admitted to sexually assaulting George but denied raping her, according to the court document. He also allegedly said that he knew his DNA would be “all over the scene.”

He lives near campus but has no affiliation to the university, police said.

Thurman is charged with first-degree murder and criminal sexual assault. At the time of George’s killing, Thurman was on parole for an armed robbery conviction. He and George did not know each other, police said.

He was denied bond at his bail hearing Tuesday. It was not immediately clear whether he entered a plea or retained an attorney.

George was an honor roll student and a member of a professional fraternity for medical-track students at the university, prosecutors said. She dreamed of becoming a physical therapist one day and had “a compassion for others,” UIC Chancellor Michael Amiridis said in a statement Monday.

“As a campus community we have shed many tears for her over the last three days,” Amiridis said. “But our collective pain pales in comparison with the ordeal her family is and will be going through for days, months and years to come. Our thoughts and our hearts are with Ruthie’s family and friends this evening.”