Three Allegheny County teenagers are charged with criminally negligent homicide after police say their friend died from overdosing on drugs they purchased in Rochester.Troopers arrested 19-year-old Robert Murray Jr., 17-year-old Spencer Carl, of Wellsville and 19-year-old Andrew Elliot, of Andover. Police say on October 22nd, the three teens, along with 18-year-old Gregory Dunne of Andover, drove to Rochester and purchased heroin. State Police say Dunne passed out in the car after snorting heroin. By the time they took him to the hospital in Allegheny County, Dunne was dead. Murray, Carl and Elliot are all being held on $50,000 bail.