Bicycle detail

Bike was parked on sidewalk directly in front of my vehicle, in my eye's view while I took a phone call in the driver side of my vehicle. Apx. 6 ft tall black Male, baggy clothes, pants, long sleeve jacket with baseball cap facing forward, afro style hair puffing out of hat rim, full cheeks and face apx 180 lbs....walked up to bicycle, I stepped out of my vehicle and told him it was my bike, he proceeded to physically steal bike and ride away on it. I ran after him, asking people to stop him (screaming at people to stop him and screaming at him myself). I could not catch the bicycle thief. A police report was file in person at SF 3rd street station an hour later.