London Breed, the mayor of San Francisco, said in a statement that “the homicide of Bob Lee is a horrible tragedy and my sympathies go out to his family and friends”.

“The Police are actively investigating what happened and will share details as soon as they can,” she added. “San Francisco is prioritizing public safety, including recently passing our budget supplemental so we have the police staffing necessary to have more police officers in our neighborhoods and to investigate violent crimes when they do occur.”

“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,” Ms Breed said.

San Francisco Police Chief William Scott issued a statement on the death of Mr Lee.

Mr Lee’s former boss Jack Dorsey was one of a many well known San Francisco tech entrepreneurs to express their shock and grief at his death.

“It’s real,” Mr Dorsey wrote on his social network Nostr. “Getting calls. Heartbreaking. Bob was instrumental to Square and Cash App. STL guy,” he wrote, in an apparent reference to Mr Lee’s hometown of St Louis.

MobileCoin CEO Joshua Goldbard wrote that Mr Lee was an “incredible human being”.

“Bob was so much more than a technologist. Bob was an artist. Everywhere he went Bob breathed love into this world. He had so much deep heartfelt love. Traveling with Bob was like seeing the world for the first time,” Mr Goldbard wrote.

“As a lifelong Bay Area resident I have more questions than answers tonight. I don’t know how to fix what’s wrong, but I know something isn’t working in our grey city,” he added.

Tributes poured in for the slain tech founder on social media.

“He was a generous decent human being who didn’t deserve to be killed,” Bill Barhydt, CEO of Abra, posted on Twitter.

“So sad to hear of @crazybob’s untimely passing,” Figma CEO Dylan Field wrote on Twitter. “I first met him in summer 2006 — he didn’t care that I was only 14 and we talked tech / geeked out about programming. We remained connected over the years and he was an early supporter of Figma. It’s so hard to believe he is gone.”

On the San Francisco Reddit forum, friends and acquaintances of Mr Lee expressed frustration at “all the needless violence in SF”.

“Something seriously needs to change in this city,” one wrote.

The tech mogul was found at 2.35am outside a luxury high-rise apartment on the 300 block of Main St near Rincon Hill and the Bay Bridge, with life-threatening stab wounds, the police said.

Lee’s friend and mixed martial arts champion Jake Shields said that the entrepreneur had just moved to Miami due to a rise in drug abuse and crime in San Francisco.

He told NewsNation that the attack was another “senseless act of violence in San Francisco”.

“He did comment on San Francisco deteriorating,” Mr Shields said, adding: “which is why he had actually just relocated to Miami.”

Bob Lee was a much-loved member of the San Francisco tech community, where he was affectionately known as Crazy Bob.

After working as an open source code developer in St Louis, Missouri, Mr Lee moved to San Francisco in his early 20s in 2004 to work as an engineer at Google, according to the San Francisco Standard. There he led the core library development for Android.

Mr Lee was headhunted by Square, becoming its 13th employee, where he helped launch the Cash App and became the payment firm’s first chief technology officer in 2011, a Linkedin profile shows.

After leaving Square in 2014, he invested in several tech startups including Clubhouse, Beeper and Faire, and the female-focused social media and networking company Present. He identified as a “stay at home dad” in an online blog post during this period.

In 2021, Mr Lee joined MobileCoin, a crypto payment firm, as its chief product officer.

Mr Lee was married to wife Krista and the couple shared two children. He had recently relocated to Miami, and was in San Francisco for a work trip when he was killed, friends said.

San Francisco Police Chief William Scott released a statement on Wednesday night giving an update on the case.

“I would like to express my deepest condolences to the family, friends, and loved ones of Mr. Lee. There is no place for this kind of violent crime against anyone in our city,” he said.

“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.”

He added that authorities will not be commenting on any evidence as the investigation is “still in the early stages”.

“Nor will we speculate on the circumstances surrounding this horrific crime,” he said.

“Although we will commit the necessary resources and personnel to this investigation, I want to assure everyone in San Francisco that our department is staffed and ready to respond to all calls for service.”

The San Francisco Police Department said in a statement that Mr Lee was found with fatal stab wounds in Downtown San Francisco between Soma and the Financial District, a block from Google’s San Francisco headquarters.

Friend and MMA fighter Jake Shields tweeted that Mr Lee appeared to have been the victim of a random mugging while out working in a “good part of the city”.

“I just found out my good friend was killed last night while walking in San Francisco. He was in the “good” part of the city and appeared to have been targeted in a random mugging/attack,” Shields wrote, adding “F*** San Francisco”.

The tweet caught the attention of Twitter CEO Elon Musk, who offered his condolences and called on San Francisco district attorney Brooke Jenkins to take tougher action against violent criminals.

“Many people I know have been severely assaulted,” Mr Musk tweeted. “Violent crime in SF is horrific and even if attackers are caught, they are often released immediately. Is the city taking stronger action to incarcerate repeat violent offenders Brooke Jenkins?”

San Francisco Police said they have not made any arrests, and haven’t provided any details of suspects.

In their statement, the SFPD said responding officers had found a 43-year-old victim with stab wounds: “Officers rendered aid and summoned medics to the scene. The victim was transported to a local hospital with life-threatening injuries. Despite efforts by first responders and medical personnel, the victim succumbed to his injuries.”

Bob Lee, who was the founder of the multibillion-dollar tech company Cash App, had relocated to Miami and was reportedly staying an extra day in San Francisco where he was stabbed to death on Tuesday.

Lee, who is survived by two young daughters and his wife Krista, was the chief product officer of San Francisco-based cryptocurrency startup MobileCoin and an active investor in companies such as SpaceX, Clubhouse, and Figma.

Lee was a much-loved member of the San Francisco tech community, where he was affectionately known as Crazy Bob.

Here is a timeline of Lee’s career and events leading up to his death: