Colin Kroll, co-founder of HQ Trivia and Vine, found dead. He was 34.

Colin Kroll, the co-founder of HQ Trivia and Vine, was found dead in his Manhattan apartment on Sunday.

Police responded to a 911 call for a welfare check at the Spring Street apartment on Sunday, a New York Police Department Spokesman told NBC News. Kroll was 34, police said.

Police found Kroll unconscious and unresponsive in a bedroom of the apartment, the spokesman said.

He was pronounced dead on the scene, police said.

A drug overdose is the suspected cause of death, police said, but an investigation is underway.

Kroll was named the chief executive of HQ Trivia, a phone-based trivia platform, in September. Prior to that he worked at Twitter.