Colin Kroll, chief executive of popular quiz app HQ Trivia, was found dead Sunday morning in his apartment in New York City, according to law enforcement. Police found his body while conducting a welfare check at the request of a concerned woman. He was 34.

The cause of Kroll’s death has yet to be confirmed by a medical examiner, police said. But several reports, including in the New York Times, have said Kroll died of an overdose and that cocaine and heroin were found near his body.

“We learned today of the passing of our friend and founder, Colin Kroll, and it’s with deep sadness that we say goodbye,” HQ Trivia tweeted Sunday. “Our thoughts go out to his family, friends and loved ones during this incredibly difficult time. "

Kroll’s trajectory in the tech world was both notable and turbulent. He helped co-found Vine in 2012 but was ousted from the company for “being a bad manager” a year and a half after it was acquired by Twitter, Recode reported. Kroll had also developed a reputation for “creepy” behavior toward women around the time of his firing in 2014, according to Recode. Kroll confirmed the circumstances of his firing to Axios and apologized for his behavior.

“As reported in the media, I was let go from Vine four years ago for poor management. It was a painful experience, but an eye-opening one that served as a catalyst for professional development and greater awareness in the office,” Kroll told Axios. “I now realize that there are things I said and did that made some feel unappreciated or uncomfortable. I apologize to those people. Today, I’m committed to building HQ Trivia into a culture-defining product and supporting the dedicated team that makes it all possible.”

In 2017, Kroll founded Intermedia Labs, the company behind HQ Trivia, along with his partner from Vine, Rus Yusupov. Some saw HQ Trivia as groundbreaking because it dictated users' engagement with it, as a live game show playable once or twice a day for roughly 15 minutes. Players answer rounds of trivia questions, and a cash prize is split among the winners, though it usually amounts to just a few dollars.

At its peak, the game frequently drew more than half a million players per round, but recent months have seen a steep drop-off in users. The company has since struggled to secure funding — in part because investors were unsettled by Kroll’s past conduct, Recode reported — and expand with new games. Kroll was named chief executive in August with hopes that he could guide the company to further success.

HQ host Scott Rogowsky stood solemnly in a black suit as he paid tribute to Kroll during Sunday night’s HQ game. Rogowsky described Kroll, or “CK” as he was known at HQ, as a “true visionary” who made his mark on the tech industry. He also stressed that Kroll was a good man and co-worker.

“Colin was a good friend and colleague, a person of compassion and generosity, and his sudden loss leaves all of us at HQ shocked,” Rogowsky said.

Yusupov praised his co-founder in a tweet after news of Kroll’s death spread, saying he would forever remember his “kind soul and big heart.”

“He made the world and internet a better place,” Yusupov tweeted.