The co-founder of the popular app HQ Trivia, Colin Kroll, has been found dead in his apartment in New York at the age of 35, police told US media.
The CEO, who also co-founded the video platform Vine, was found by police after his girlfriend reportedly asked them to check on him.
The death is being investigated as a suspected drugs overdose, police say.
HQ Trivia, a live trivia game on mobiles, became hugely popular, but its appeal waned this year.
Officers of the New York Police Department went to Mr Kroll’s flat in Manhattan to carry out a welfare check and found his body along with drugs paraphernalia nearby, TMZ reported in the initial media coverage of his death.
Police confirmed the death in calls to other media outlets.
Mr Kroll and Rus Yusupov co-founded HQ Trivia, with Mr Kroll named CEO this September.
It was launched in the US last year.
The free app live-streams quiz shows, with a pot of money – often thousands of dollars – available to split between winners.
The quiz show was guest-hosted by some big names, from Jimmy Kimmel to Bert from Sesame Street.
Its popularity faded this year, dropping out of the App Store’s list of top 100 apps.
Mr Kroll was also a co-founder of Vine, a six-second video streaming service that was bought out by Twitter in 2012 for $30m (£24m).
Vine announced in December 2016 that Twitter was discontinuing the mobile app.