A 15-year-old boy has been arrested for allegedly fatally stabbing his grandmother and injuring his mother in Selden, New York, according to police.

       Vanessa Chendemi was allegedly stabbed by her son at about 9:45 p.m. Monday after which she ran out of her house and a passing motorist stopped to offer assistance, the Suffolk County Police Department said. Upon arriving at the scene, officers said they found 56-year-old Concetta Chendemi with stab wounds in the residence.

       She was pronounced dead at the scene, according to police.

       Vanessa Chendemi, 36, was transported to an area hospital and is in stable condition, Suffolk County police said.

       The suspect fled the scene after the stabbing, police said. He was later arrested at around 11:20 p.m.

       The accused stabber -- who has not been identified by police because he is a minor -- has been charged with second-degree murder and attempted murder.

       He is scheduled to be arraigned on Tuesday.