(AP) — Details of how tech executive Bob Lee came to be fatally stabbed in downtown San Francisco early Tuesday were scarce as friends and family continued to mourn the man they called brilliant, kind and unlike others in the industry.

San Francisco police found Lee, 43, on the sidewalk in front of a condominium building with stab wounds shortly after 2:35 a.m. Tuesday.

He was taken to a hospital where he died.

The neighborhood where the stabbing occurred is near the Embarcadero waterfront and full of tech offices, towering condominium buildings and not much else late at night.

Lee created the mobile payment service Cash App and was the chief product officer for cryptocurrency MobileCoin at the time of his death. He was previously the chief technology officer of the payment company Square, which became Block in late 2021.

Lee was apparently in San Francisco for a visit after moving to Miami in October, his father, Rick Lee, said on social media. The two had been living in the San Francisco suburb of Mill Valley.

“Bob would give you the shirt off his back,” Rick Lee wrote. “He would never look down on anyone and adhered to a strict no-judgment philosophy. Bobby worked harder than anyone and was the smartest person I have ever known.”

San Francisco police have provided little information, saying the investigation is still early.

“Because of this we are not commenting on evidence, nor will we speculate on the circumstances surrounding this horrific crime,” Police Chief Bill Scott said in a statement Wednesday.

Lee’s death further enflamed debate over public safety in San Francisco and its moribund downtown, which has not yet bounced back from the pandemic. Twitter’s owner Elon Musk took to the social media site to post that “violent crime in SF is horrific and even if attackers are caught, they are often released immediately.” Musk tagged the city’s district attorney in the post.

San Francisco suffers from property crime more than violent crime such as murder, rape, robbery and assault.

In a statement, San Francisco Mayor London Breed called the homicide “a horrible tragedy” and said that the city is prioritizing public safety.

“I’m confident that when the police make an arrest in cases like this, our district attorney will do what’s necessary to hold any individuals accountable for their actions,” she said.

MobileCoin CEO Josh Goldbard said in a string of tweets Wednesday that Lee’s energy was infectious and his mind kaleidoscopic.

“He had so much deep heartfelt love,” Goldbard wrote. “Traveling with Bob was like seeing the world for the first time.”

Lee came to MobileCoin as an early stage investor and advisor, then became chief product officer and helped launch the Moby app, Goldbard said. Lee was the chief technology officer at digital payments company Square in 2013 when it launched a money transfer application now known as Cash App.

Among the tech leaders to share their devastation about Lee’s death was venture capitalist Wesley Chan, co-founder of FPV Ventures. Chan said he befriended Lee more than a decade ago when they both worked at Google, at a time when software engineers like Lee were helping to build the Android smartphone operating system before its 2008 release.

“He was an incredibly iconic founder in the tech world,” Chan said by phone Wednesday. “He wrote large parts of Android when he was at Google. He became the CTO of Square and helped build Cash App. His resume reads something like a Fortune cover article.”

But Chan said Lee was also generous in helping to coach and champion other engineers and tech entrepreneurs who’d call on him for advice. And he was modest about his key role in developing successful products, such as the widely used Cash App.

“With everything that Bob worked on, it was always a pleasant surprise,” Chan said. “That’s one of the things I loved about him. He was always humble about it, he’d say, ‘Oh, I don’t know if it’s going to work or not, but we’ll try.'”