MILFORD, Conn. (CBSnewYork/AP) — A Connecticut teenager has been sentenced to 25 years in prison for stabbing a classmate to death at their high school because he was upset she turned down his prom invitation.

A judge handed down the sentence to 19-year-old Christopher Plaskon on Monday in Milford Superior Court.

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Plaskon pleaded no contest to murder in March in the killing of 16-year-old Maren Sanchez inside Jonathan Law High School in Milford in April 2014. His family has said he was upset Sanchez turned down his prom invitation.

Maren Sanchez is seen in the dress she planned on wearing to her prom. (credit: Image via Facebook)

Maren Sanchez is seen in the dress she planned on wearing to her prom. (credit: Image via Facebook)

A witness saw Plaskon on top of Sanchez during the attack and tried unsuccessfully to pull him away and another saw him discard a bloody knife, according to a police affidavit.

Plaskon’s attorneys have said he showed signs of psychosis and they considered an insanity defense.

“I don’t think this was an issue of a young man being rejected for the prom, I think this was an issue of a boy who had quietly and silently suffered from some degree of mental illness,” attorney Richard Meehan told WCBS 880’s Fran Schneidau.

As CBS2’s Scott Rapoport reported, Sanchez’s family said the sentence isn’t enough.

In the court room, off-camera in front of the judge, the victim’s mother Donna Cimarelli refused to discuss Plaskon.

Instead, she described her daughter as ‘the love of my life,’ ‘my best friend,’ and said ‘she was destined for greatness.’

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Later she spoke to reporters for the first time.

“My feelings are that Maren is in my soul. She walks with me every day,” she said.

Meehan said Plaskon will be eligible for release after serving 13 years because he was a minor when the stabbing occurred.

It’s troubling news for the victim’s family.

“The message that is sends is if you commit a crime as heinous as murder in the state of Connecticut, you’re doing very little time,” Maren’s father Jose Sanchez said.

They said the sentence left them with no sense of closure or comfort.

Plaskon is supposed to stay at a youth prison in Chesire until he turns 22, then he’ll be transferred to an adult facility.

Sanchez’s parents filed a lawsuit accusing the school system of negligence, saying she told a guidance counselor that Plaskon was troubled and capable of hurting others. School officials have declined to comment.

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