Bicycle detail

After going to the Gym, I stopped at Safeway thinking I could lock up my bike and run in real quick to get something to eat. As there were a lot of people coming in & out, and it being the middle of the day. I went in and came out to find my bike lock cut where I parked it, and a customer saw me and said "did somebody just steal your bike!?" I said, "Yes!" and she said "I JUST saw him, he went that way!" and I saw him ride across the parking lot. I tried to chase after him, and he turned and saw me and sped up. I then yelled "HE STOLE MY BIKE!" several times to let other people know. He made it down the block and turned off before I could see where he went. Police were notified. Guy was wearing baggy pants, a hooded sweatshirt and a light white/grey colored backpack.