Tech executive and investor Bob Lee, who helped create Android and Cash App, was stabbed to death in San Francisco on Tuesday night.
Bob Lee, 43, was attacked in the city's plush downtown residential Rincon Hill neighborhood at 2.35am on Tuesday.
Police were called to the 300 block of Main Street near the entrance of a high-rise close to the waterfront and found the dad-of-two suffering from multiple stab wounds.
Friends told the San Francisco Standard that he had been visiting the area for business and decided to stay an extra day when he was stabbed.
Twitter and Tesla CEO Elon Musk also commented on the horrific incident, asking the San Francisco DA what she is doing to 'incarcerate repeated violent offenders'.
He said: 'Very sorry to hear that. 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.
'Is the city taking stronger action to incarcerate repeat violent offenders Brooke Jenkins?'
Former MMA fighter Jake Shields remembered the tech executive as a "loyal friend", with Musk responding to his Tweet.
Shields claimed that Lee was 'targeted' in a 'random mugging and attack' despite being in a 'good ' part of the city.
The tech mogul had been living in a $1.8million apartment in Miami, while his wife Krista appears to still be living in San Francisco.
Authorities confirmed that he was rushed to hospital but died from his injuries in the early hours.
Officials have yet to make an arrest, and San Francisco Police have not released any details of a suspect.
In a statement, they said: 'Officers rendered aid and summoned medics to the scene. The victim was transported to a local hospital with life-threatening injuries,' police said in a statement.
'Despite efforts by first responders and medical personnel, the victim succumbed to his injuries.'
Lee, who was dubbed 'Crazy Bob' by friends, was an active investor in numerous companies, such as SpaceX, Clubhouse and Figma.
Heartbroken friends and colleagues paid tribute to the tech executive, with Joshua Goldbard saying: 'My heart is broken tonight'.
He added: 'Bob was a force of nature. Helped to birth Android and CashApp into our world.
'Moby was his dream: a privacy-protecting wallet for the 21st Century. I will miss him every day.'
Bill Barhydt added: 'Bob was a dad, the former CTO of Square where he created Cash App & CTO of Mobile Coin.
'He was a generous decent human being who didn't deserve to be killed.'
Co-Founder of Twitter Jack Dorsey said: 'It's real. Getting calls. Heartbreaking. Bob was instrumental to Square and Cash App. STL guy.'
The founder of cryptocurrency and payments firm MobileCoin had worked with Lee for two years, where he served as chief product officer since November 2021.
Lee had formerly been chief technology officer at Square - which has recently renamed itself to Block - when it had developed and launched Square Cash in 2013.
Since that time, the brand has grown into Cash App, with tens of millions of users in the US and the UK.
Prior to that, Lee had worked as a software engineer at Google from 2004 to 2010, where he helped design the core library for Android.
So far this year in the city there have been 39 murders, which is up two from this time last year as an increase in crime is leaving residents worried.
Democrat Mayor London Breed said in February she is requesting nearly $30 million in additional funding for the city's police force.
The San Francisco Police Department has encountered rising overtime costs for current officers as the force is experiencing a shortage of workers.
Between 2021 and 2022, the department saw a 121 percent increase in total overtime, according to KPIX.
SFPD officials have also been making targeted attempts to address crime in certain pockets in the city which are prone to incidents.
The San Francisco Police Department is currently experiencing a shortage of 541 officers.
Police are urging anyone with information to come forward by calling the SFPD tip-line 415-575-4444.
Comment: Could this have anything to do with it?: Defunding police has turned 'progressive' San Francisco into a haven for shoplifters, thieves and drug addicts