Co-founder of the popular app HQ Trivia Colin Kroll has been found dead in his apartment in New York at the age of 34.
The CEO, who also co-founded the video platform Vine, was found by police after his girlfriend reportedly asked them to check on him.
An HQ spokesperson confirmed the death "with deep sadness".
HQ Trivia, a live trivia game on mobiles, became hugely popular, although 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.
The HQ statement read: "We learned today of the passing of our friend and founder, Colin Kroll, and it's with deep sadness that we say goodbye. Our thoughts go out to his family, friends and loved ones during this incredibly difficult time."
The company confirmed Mr Kroll's age after police had initially said 35.
Mr Kroll's father, Alan, told the New York Times: "He had so much talent and had accomplished so much at such a young age. It truly is a waste."
Mr Kroll co-founded HQ Trivia with Rus Yusupov. Mr Yusupov paid tribute on Twitter:
So sad to hear about the passing of my friend and co-founder Colin Kroll. My thoughts & prayers go out to his loved ones. I will forever remember him for his kind soul and big heart. He made the world and internet a better place. Rest in peace, brother.— Rus (@rus) December 16, 2018
HQ Trivia was launched in the US last year and Mr Kroll was named CEO this September.
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 US$30m.
Vine announced in December 2016 that Twitter was discontinuing the mobile app.