A convicted criminal out on parole for armed robbery has been charged with killing University of Illinois at Chicago student Ruth George, according to police.

George, 19, was found dead at a parking garage on the school’s campus on Saturday. UIC Police took a man into custody who was seen on surveillance video following the student into the garage over the weekend. After initially calling him a “person of interest,” police charged Donald Thurman with first-degree murder and aggravated assault on Monday afternoon.

George’s death was ruled a homicide by strangulation on Sunday, according to the Cook County Medical Examiner’s Office.

Authorities said Thurman, 26, lived near the UIC campus, but had no affiliation to the school. He also had no connection to George, police said.

Thurman was previously convicted of armed robbery and sentenced to six years in prison, but was released in December 2018 after serving only two years. He was on parole at the time of the alleged killing of George.

George entered the parking garage early Saturday at 1:35 a.m., with the suspect following right behind her, police said. Thurman is allegedly seen exiting the structure at 2:10 a.m. George’s family became concerned when they did not hear from her Saturday morning and police followed a ping from her cellphone to find her unconscious in her car in the parking garage.

Thurman was taken into custody on Sunday and he allegedly confessed to “this horrific crime” that afternoon, police said.

UIC Chancellor Michael Amiridis said the campus was “struggling with this senseless loss of life” in a statement Monday.

“Ruthie was an Honors College student who focused on her studies, a young woman who dreamed of becoming a physical therapist to heal people and who was always there to lend a hand to her peers, many of whom would seek her out because of her compassion for others,” he said.

“As a campus community we have shed many tears for her over the last three days,” Amiridis added. “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.”

ABC News’ Darren Reynolds and Courtney Condron contributed to this report.