A Connecticut teenager stabbed and killed his classmate who allegedly turned down his invitation to the junior prom. He pleaded no contest to murder Monday, and prosecutors say they will seek a 25-year prison term. 

Christopher Plaskon, 18, accepted a plea bargain in Milford Superior Court, according to Fox News. Sentencing is set for June 6.

Plaskon stabbed 16-year-old Maren Sanchez in the throat, neck and trunk at Jonathan Law High School in Milford on April 25, 2014. His family and friends said he became upset that Sanchez turned down his prom invitation.

Plaskon was held at a psychiatric hospital after the stabbing. His attorneys said they were considering an insanity defense. His mental health has been evaluated by both sides, according to New Haven Register. 

According to Fox News, a witness tried to pull Plaskon off Sanchez during the attack that happened in a first-floor hallway at about 7:15 a.m. on the day of the junior prom.

Plaskon was taken to the principle's office in bloody clothing and told police, "I did it. Just arrest me," according to the affidavit.

Despite the paramedics' attempt in saving Sanchez, she was pronounced dead at a hospital shortly afterward.

Edward Gavin, of Meehan, Meehan & Gavin law firm in Bridgeport, has said the defense doctors found mental disease or defect at a press conference outside the courthouse.

Plaskon is on medication and stable, and "is doing the best he can," said Gavin.

With a new juvenile justice law that calls for a review of long prison sentences for younger offenders could mean Plaskon could be released after serving 13 years.

Plaskon would be eligible for parole after serving 60 percent of his sentence, taking the 25-year sentence down to 15 years, his lawyer said.

"And he has two years in," Gavin said. "So he would be parole-eligible. It's not a guarantee. That's up to a parole board to go ahead and decide. But Christopher could potentially be released in 13 years."

Plaskon, now 18, pleaded no contest to a charge of murder, meaning he did not admit guilt but that he did not want to fight  the charge. According to Gavin, Plaskon and Sanchez were friends and grew up together.