A 16-year-old Mount Vernon High School student was stabbed to death just blocks away from his house in Mount Vernon Monday night, police say.

Two police officers were on routine patrol on North 8th Street at around 10:30 p.m. when they saw Douglas Williams staggering to the ground, bleeding from stab wounds to his chest and side. The teen was rushed to Jacobi Medical Center, where he had emergency surgery. Williams was pronounced dead early Tuesday morning.

Williams' relatives say the teen was walking home from a friend's house when he was fatally stabbed. They don't know why it happened, or who would have wanted to kill him.

"He was not a street person," says Williams' cousin Eric Thomas.

Police have yet to release a motive behind Williams' murder, but they say it was not a random act of violence.