Bob Lee, the founder of the mobile payment company Cash App and former employee of Square, has died after being stabbed near downtown San Francisco on Tuesday. The police responded to a stabbing report at around 2:35 a.m. and found Lee with apparent stab wounds. He was taken to a hospital where he later died. The police department’s homicide detail is investigating the case, and Police Chief Bill Scott has called it a horrific crime.

Lee, 43, was the chief product officer of the cryptocurrency firm MobileCoin at the time of his death. He previously worked as the chief technology officer of Square, which is now known as Block. Lee was also the creator of Cash App, a money transfer service. He was an investor in several tech companies, including Elon Musk’s SpaceX venture and the social audio app Clubhouse.

Lee’s father, Richard Lee, described him as the smartest person he ever knew and said that he would be missed by all who knew him. Lee’s brother, Tim Oliver Lee, expressed his sadness on Facebook, saying that he had lost part of himself. Joshua Goldbard, the founder and CEO of MobileCoin, praised Lee’s business acumen and described him as a “dynamo” and a “force of nature.”

The World Health Organization confirmed that Lee had offered his support and expertise during the pandemic and had built a large part of the server for the WHO Covid-19 App. The police chief offered his condolences to Lee’s family and friends and assured everyone that investigators are working tirelessly to make an arrest and bring justice to Lee and his loved ones.