Bob Lee, a technology executive who founded the mobile payment company Cash App and previously worked at Square, died Tuesday after he was stabbed near downtown San Francisco, according to his family and police.

San Francisco police said officers responded to a report of a stabbing around 2:35 a.m. Tuesday. The officers found Robert Lee, 43, with apparent stab wounds. He was taken to a hospital and died of his injuries, police said.

Police Chief Bill Scott said in a statement Wednesday night that the investigation is in its early stages and he called it a horrific crime.

The incident is under investigation by the police department’s homicide detail, the department said.

Lee had been working as the chief product officer of the cryptocurrency company MobileCoin. He was previously chief technology officer of Square (now known as Block), a financial technology start-up co-founded by the former Twitter chief Jack Dorsey. 

Lee went on to create Cash App, a money transfer service.

“Bobby worked harder than anyone and was the smartest person I have ever known. He will be missed by all those that knew him,” his father, Richard Lee, said in a Facebook post, which was accompanied by a news article about the stabbing. “Thank you to those who have reached out in support.”

The father and son had been living in Miami since October after moving from California, Richard Lee said in the post. They had grown especially close after Bob Lee’s mother died in 2019. It wasn't immediately clear why Lee was back in the Bay Area.

"I'm so saddened and disheartened to lose my brother," Tim Oliver Lee wrote on Facebook. "He really was the best of us. I was so fortunate to grow up with him, and I feel like I've lost part of myself."

In a statement Wednesday, Joshua Goldbard, the founder and CEO of MobileCoin, said Bob Lee “passed away yesterday” and praised his business acumen. He did not specify Lee’s cause of death.

“Bob was a dynamo, a force of nature. Bob was the genuine article,” Goldbard said. “He was made for the world that is being born right now, he was a child of dreams, and whatever he imagined, no matter how crazy, he made real.”

Goldbard said in a Twitter thread that Lee was “like a brother to me,” and he praised Lee as a “brilliant” visionary with a “kaleidoscopic” mind.

The World Health Organization confirmed to NBC News on Wednesday that Lee offered his “support and expertise” during the pandemic, saying in a statement that “Bob built a large part of the server for the WHO Covid-19 App.”

Lee also was an investor in Elon Musk’s SpaceX venture, as well as other tech firms, such as the social audio app Clubhouse, according to his LinkedIn profile. He used the handle “crazybob” for his LinkedIn and Twitter pages.

Scott, the police chief, offered his condolences Wednesday night to Lee's family and friends.

“There is no place for this kind of violent crime against anyone in our city,” Scott said in the statement. “I want to assure everyone that our investigators are working tirelessly to make an arrest and bring justice to Mr. Lee and his loved ones, just as we try to do on every homicide that occurs in our city.”

The fatal stabbing could intensify scrutiny of public safety issues in San Francisco, where residents and business owners have grown increasingly concerned about violent crimes and thefts. Mayor London Breed has pledged to crack down on crime.

San Francisco has had 12 homicides since the beginning of the year, according to data compiled by the police department. In the same period last year, it had 10 homicides.

Lee’s family, friends and colleagues paid tribute to him.

Krista Lee called her former husband “the most incredible and beautiful human being” and said that “he was everyone’s best friend.”

They had two children, Damien, 17, and Scout, 14. Damien Lee said his father was a down-to-earth person who always listened.

“He was such a special person in this world. I’m so sad that he left us so early,” Damien Lee said in a statement.

In a statement shared by her mother, Scout Lee said she was "devastated that somebody would be so cruel to take away my father's life."

"He was the best man and an even better father, if you ask anyone who knew him they’d always say that he was the best and they would always have some amazing story to share about their experiences with him," she said.

"I will forever miss my dad and be shattered by his death because he was not only my father but one of my best friends," she said later in the statement.

The former MMA fighter Jake Shields remembered him as a “loyal friend.” In a response to one of Shields’ tweets, Musk said he was “very sorry” to learn of Lee’s death.

Dorsey, the former CEO of Twitter, called Lee’s death “heartbreaking” on the social media platform Nostr. “Bob was instrumental to Square and Cash App,” Dorsey wrote.

Joshua Bloch, a friend who worked with Lee at Google in the late 2000s, remembered him as a magnetic person who “always had a huge smile on his face” and “constantly lived life to the fullest.”

In a phone interview Wednesday, Bloch recalled that Lee was a tech “autodidact” who could seemingly “do anything he wanted,” adding, “I don’t think he realized how special he was.”