Hayley McNeff's cause of death has been revealed. The fitness influencer died from "acute intoxication due to the combined effects of heroin, fentanyl, 4-ANPP, cocaine and norbuprenorphine," Director of Communications for Massachusetts's Executive Office of Public Safety and Security, Brenna Galvin, told People in a statement on Monday, November 10. Galvin ruled McNeff's death an accident, per the report. Us Weekly has reached out for comment. News broke in August that McNeff, a bodybuilder, died at the age of 37.