We still don't know the full circumstances of the fatal stabbing that took place on Main Street in San Francisco early Tuesday, but news quickly spread Tuesday afternoon that the victim was a well known tech founder.

The victim was Bob Lee, 43, the chief product officer of MobileCoin Inc. and former chief technology officer at Square (now Block), and Jack Dorsey confirmed the death to KTVU. "It's real. Getting calls. Heartbreaking," Dorsey said.

Lee, whose Twitter handle was @crazybob, founded CashApp, and friends in the tech world were tweeting overnight about his shocking death. As an engineer, Lee was also credited with helping create Google's Android operating system.

"The thing is, Bob was so much more than a technologist," said MobileCoin founder Joshua Goldbard. "Bob was an artist. Everywhere he went Bob breathed love into this world. He had so much deep heartfelt love."

"Bob was a dad," said Bill Barhydt, CEO of Abra, on Twitter. "He was a generous decent human being who didn’t deserve to be killed."

The Chronicle reports, via accounts of friends on social media, that Lee was back in town visiting after moving to Miami last year. It was previously reported that the victim in the stabbing was a resident of Mill Valley, but perhaps that came from an outdated driver's license — and Lee reportedly sold his Mill Valley home for $4.4 million last year.

The SF Standard reports that surveillance footage from the scene appeared to show Lee stumbling, wounded, up Main Street away from the Bay Bridge aroudn 2:30 a.m. Tuesday. He may have been looking for help, and was clutching his side while holding his phone with the other — "Lee then crosses the intersection at Harrison Street toward a parked white Camry with its lights flashing, the video appears to show. Lee lifts his shirt — as if to show the driver his wound and ask for help — and then falls to the ground after the car drives away," the Standard reports. He then apparently stumbled toward the Portside condominium building where he collapsed.

Elon Musk, who may or may not have known Lee personally, used the case to decry the state of San Francisco's streets and the city's lack of toughness on crime. He was replying to former MMA fighter Jake Shields who claimed to be a "good friend" of Lee, who he said was in the "'good' part of town" and might have been mugged, adding "Fuck San Francisco."

Says Musk, "Many people I know have been severely assaulted. Violent crime in SF is horrific and even if attackers are caught, they are often released immediately." And he used the moment to @-message DA Brooke Jenkins, saying "Is the city taking stronger action to incarcerate repeat violent offenders."

In reply this morning, Jenkins tweeted, "We do not tolerate these horrific acts of violence in San Francisco."

The killing of Lee was San Francisco's 13th homicide of the year to date.

Anyone with information about the stabbing is asked to call the SFPD 24-hour-tip line at 415-575-4444, or text a tip to TIP411 and start the message with SFPD. Anyone who provides a tip may stay anonymous.

Related: Marin Man Fatally Stabbed In SoMa, Near Embarcadero

Photo via MobileCoin