SAN FRANCISCO -- A man stabbed to death early Tuesday morning near downtown San Francisco was well-known tech executive Bob Lee, founder of Cash App and the former chief technology officer of Square, sources told KPIX.Officers responded at about 2:35 a.m. to a report of a stabbing in the 300 block of Main Street in the city's Rincon Hill neighborhood and arrived to find the victim, who was taken to a hospital and succumbed to his injuries there, police said. The city's medical examiner's office had not yet identified the victim as of Tuesday evening, but friends of Lee told KPIX he was the victim. The 43-year-old Lee was the Chief Product Officer of San Francisco-based cryptocurrency startup MobileCoin.On Twitter Tuesday evening, a flood of messages were posted eulogizing Lee, many including his @crazybob Twitter handle.No arrest has been made in the case and San Francisco police have not released any suspect details.Anyone with information about the fatal stabbing was asked to call the Police Department's tip line at (415) 575-4444 or to send a tip by text message to TIP411 with "SFPD" at the start of the message.