Kevin Loibl, the man Orlando Police detectives say fatally shot Grimmie on June 11 as she was signing autographs after a concert, spent most of his time watching Grimmie on YouTube and that he constantly monitored her social media accounts, his friend, Cory Dennington, told detectives.
Dennington worked with Loibl at a Best Buy store in the St. Petersburg, Florida, area and described himself as Loibl's only friend.
Loibl "made it clear he watched everything having to do with her," Dennington told detectives.
Dennington became concerned enough with Loibl's obsession with Grimmie that he told their boss at Best Buy about it, according to the police report.
The boss, Luke Dahl, told detectives he never spoke to Loibl directly about the infatuation but said he had seen Loibl watching Grimmie's YouTube videos at work.
Dahl described Loibl as "socially awkward, detached." He also said Loibl lacked social skills and worked in the back of the store on computers so he didn't interact with customers with his part-time job.
Loibl, 27, didn't have any previous criminal history, detectives said. He lived at home with his father and brother, and they told detectives they were unaware with his obsession.
His father, Paul Loibl, told detectives that his son "lived like hermit," hardly leaving his room except to go to his job.
Two representatives for Grimmie's management company didn't immediately respond to an email seeking comment.
Thousands of friends and fans said farewell to Grimmie last week in Medford, New Jersey, where her family lived before moving to southern California in 2012.
Grimmie's team posted an "In Loving Memory" video to YouTube Friday. Watch it in full below: