Accused Idaho killer Bryan Kohberger allegedly had multiple photos of one of the female victims on his phone — suggesting that he had been specifically “paying attention” to her, a source connected to the case said this week.

The images were found on Kohberger’s phone when it was seized by investigators after he was arrested in late December for the Nov. 13 stabbing deaths of Kaylee Goncalves, 21, Madison Mogen, 21, Xana Kernodle, 20, and Ethan Chapin, 20, the source told PEOPLE.

Though the source did not identify which of the female victims was in the pictures, they confirmed that Kohberger had “more than one” photo of her.

“It was clear that he was paying attention to her,” they said.

At the time of his arrest, Kohberger, 28, was a doctoral student in criminology at Washington State University in Pullman, about 15 minutes from the off-campus home where the students were killed.

Though investigators are tight-lipped on the Pennsylvania native’s possible ties to the victims, cellphone data included in a probable cause affidavit revealed that he may have stalked the neighborhood multiple times in the months before the murders.

The affidavit also included touch DNA evidence linking Kohberger to a knife sheath at the scene, as well as reports from surviving roommate Dylan Mortensen, who came face to face with the alleged killer as he left the property.

News of Kohberger’s alleged camera roll evidence comes shortly after the New York Times reported that he was fired from his teaching assistant position amid allegations that he behaved inappropriately with female students.

According to two anonymous sources, Kohberger followed at least one student to her car.

In the nearly two months since he was arrested at his parents’ home, past classmates and acquaintances have recalled Kohberger as a “creepy” loner who morphed from a bullied teen into an aggressive adult.

Jordan Serulneck, the owner of Seven Sirens Brewing Company in Bethlehem, Pa., said last month that Kohberger had a history of harassing women at his bar.

“He’ll have two or three beers and then just get a little too comfortable,” he recalled, noting that Kohberger got “upset” when the women rebuffed his advances.

As of late February, Kohberger remains in custody in Latah County. He is expected back in court for a hearing beginning June 26.