(CNN)Brandon Clark, who is accused of killing 17-year-old Bianca Devins, has pleaded not guilty to second-degree murder, according to his attorney, Luke Nebush of the Oneida County Public Defender's Office.Bianca Devins As required by the judge, the District Attorney's office made an offer for Clark to plead guilty and serve 25 years to life, but Clark rejected the offer, said Oneida County District Attorney Scott McNamara. Clark, 21, is accused of killing Devins on July 14 and then posting gruesome pictures of her body online. She was found with her throat slashed. Clark was hospitalized after he stabbed himself in the neck at the time of arrest, but is now is being held at Oneida County Correctional Facility, according to Utica police Lt. Bryan Coromato. A motive remains uncertain Police said Clark and Devins met on Instagram about two months ago and grew close. Authorities said they were driving back from a concert in New York City when an argument between the two precipitated her death. "He's with her in the car. The attack happens in the vehicle," Coromato said Wednesday. "The motive is still something we are looking into. ... We are looking at the dynamics of the relationship, what the relationship meant to him, what the relationship meant to her. There was a relationship, and it potentially was more serious to him than it was to her." Horrified gamers helped contact police Devins, a recent high school graduate, had amassed a large social media following across several platforms. She was especially well-known in the online gaming community. And it was on a social app for gamers, Discord, where Clark posted photos of Devins' body, police say. Members of Discord who saw the ghastly images contacted the Utica Police Department. "The first call was from Tennessee," Coromato said. "Someone on Discord saw the picture of her. She appeared to be deceased with a large wound on her neck, and it said her name and Utica, New York." Discord said it is working with investigators. "We are shocked and deeply saddened by this terrible situation," the company said. "We are working closely with law enforcement to provide any assistance we can. In the meantime, our hearts go out to Bianca's family and loved ones." The suspect stabbed himself and took selfies, police say Utica police said they received several 911 calls about a suicidal man who said he killed a woman. When an officer arrived and found Clark, the suspect started stabbing his throat with a large knife, police said. He didn't respond to the officer's verbal commands, Coromato said. "He's posting photos of himself," the police spokesman said after watching bodycam footage from the scene. Clark was eventually hospitalized and underwent emergency surgery. The slain teen planned to attend college in the fall Devins' family issued a statement thanking loved ones for their support and prayers "Bianca, age 17, was a talented artist, a loving sister, daughter, and cousin, and a wonderful young girl, taken from us all too soon," the statement read. "She is now looking down on us, as she joins her cat, Belle, in heaven." Devins had planned to attend Mohawk Valley Community College in Utica in the fall, her family said. "Bianca's smile brightened our lives. She will always be remembered as our princess."
CNN's Carma Hassan, Scottie Andrew, and Holly Yan contributed to this report.