Police reported that Lee was attacked and stabbed by an unknown assailant. The incident happened at 3:30 a.m. under unclear circumstances in the 300 block of Main Street in San Francisco.
Medics tried to save Lee and took him to the hospital, where he died of his injuries. No arrests or detentions were made in the case. The San Francisco Police Department has not shared any additional details with the media.
"Many people I know have been severely assaulted," Musk tweeted, slamming the city for the tragedy. "Violent crime in SF is horrific and even if attackers are caught, they are often released immediately."
Lee was a product director at MobileCoin. He began his career as a Google developer on the Core Library team for Android. After leaving Google, Lee joined Jack Dorsey's Square and helped create Cash App, a payment service.
In addition to developing and managing tech departments at IT companies, Lee has been involved in investing in various startups and helping the programming community.
"Bob was a force of nature. Helped to birth Android and CashApp into our world," MobileCoin CEO Joshua Goldbard US media. "Moby was his dream: a privacy-protecting wallet for the 21st Century. I will miss him every day."
Following the news of Lee's death, the development community and executives of many IT companies said it was a serious loss, and his untimely death was a heartbreaking event for many.