15-year-old boy accused of fatally stabbing grandmother on Long Island; mother injured

LONG ISLAND - A 15-year-old boy was arrested Monday night on Long Island after police said he fatally stabbed his grandmother. The boy is also accused of stabbing his mother, who was injured in the incident.

What we know:

According to police, after allegedly being stabbed by her son, 36-year-old Vanessa Chendemi ran out of her Old Town Road home around 9:50 p.m. Police said when a passing driver stopped to help, Vanessa got into the vehicle and called 911.

When officers arrived at the home, they found 56-year-old Concetta Chendemi insidewith stab wounds. She was pronounced dead at the scene. 

Vanessa was taken to a hospital in stable condition with stab wounds to her arm, back, neck and face. She's expected to survive. Two chef knives were recovered at the scene, police said.

The boy fled the scene after the stabbing, but was arrested just before 11:30 p.m. at Dare Road and Buckskin Lane in Selden, police said.

He was charged with murder in the second degree, as well as attempted murder. His name is being withheld due to his age. He was scheduled to be arraigned on Tuesday at First District Court in Central Islip.

The home is a split-family house. The boy, as well as the grandmother and mother, lived on the first floor.

What we don't know:

The exact motive for the stabbings was unclear, though police said there was an argument over some sort of content on the boy’s computer.