Joey Bonavitacola died suddenly on Sept. 23 from the combined effects of heroin, cocaine and alcohol, according to the Maryland Medical Examiner's office.
A spokesperson for the office said the manner of death was undetermined.
Bonavitacola, who was 18 at the time of his death, graduated from Howard High School in 2012 and was a star running back on the Howard High football team.
He was from Elkridge.
Requests for comment from Howard High School and the Howard football team were declined by the school's athletic director, Michael Duffy.
Police declined to provide any information surrounding the circumstances of Bonavitacola's death because it was deemed not a criminal matter, according to a Howard County police spokesperson.
Attempts to contact the Bonavitacola family on Tuesday were unsuccessful.
In his senior season, Bonavitacola rushed for 700 yards and 10 touchdowns, helping the Lions qualify for the playoffs, according to an article in Explore Howard.
The news of Bonavitacola's death shook the Howard High community. On the Howard football team's Facebook page, families from around Howard County offered their prayers to Bonavitacola's family.
Lions football coach Bruce Strunk has said of Bonavitacola: "...no one had the kind of heart that he did on the field," reported the Howard County Times, which described the teen as "popular" and a "star."
The Lions' defensive coordinator Doug Caplan told Ellicott City Patch that Bonavitacola was "quick" after the player, a junior at the time, had a breakout game with two touchdowns, 16 carries and 209 yards rushing against Oakland Mills in fall 2010.