The family of a teenager who was stabbed to death by a classmate inside her Connecticut high school for rejecting his prom invitation has filed a lawsuit alleging the school didn't adequately respond to signs the boy was capable of violence.

The lawsuit was filed Tuesday by the mother of the victim, 16-year-old Maren Sanchez, who was killed at Jonathan Law High School in Milford in April 2014.

The lawsuit alleges that Maren had told the guidance department that the assailant, Christopher Plaskon, was emotionally disturbed.

Plaskon, now 18, pleaded no contest to murder earlier this month.

Plaskon, his relatives, the city of Milford and its board of education are defendants in the suit.

A spokeswoman for the Milford school system said she couldn't immediately comment.