Friends and former colleagues in the tech world mourned the death of Cash App founder Bob Lee on Wednesday, just hours after the CEO was stabbed to death in an apparently random attack.

Lee, 43, was killed early Tuesday morning in San Francisco, and his attacker has yet to be identified or apprehended. Twitter CEO Elon Musk called the crime situation in San Francisco "horrific" after hearing about the attack.

"Very sorry to hear that," Musk told a user referencing Lee's killing. "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."

Musk went on to tag the San Francisco district attorney to ask what she was doing to lower violent crime rates.

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Jack Dorsey, who owns the parent company of Cash App, also expressed his condolences after confirming the murder on social media.

"It’s real. Getting calls. Heartbreaking," Dorsey announced. "Bob was instrumental to Square and Cash App. STL guy."

A number of other tech CEOs joined in mourning Lee after news of his death broke. Lee was the father to two daughters.

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"I’m still in shock," a friend of the slain executive told the San Francisco Chronicle. "No way he did anything to provoke this and I feel like he would just hand his money and watch to a mugger."

"I just got devastating news that our friend Bob Lee was killed in SF early today," Abra Global CEO Bill Barhydt wrote on Twitter. "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."

San Francisco police are still investigating the attack on Lee. Police arrived soon after the 2:35 a.m. stabbing and rushed Lee to the hospital, but he succumbed to his injuries.