Authorities arrest man seen on surveillance video beating up a man at a gas station

SAN MARCOS, CA - This man -- 32-year-old Fredrick Cato from Carlsbad is behind bars tonight.

On September 28 -- he is seen here on surveillance video walking into chevron, punched a 56-year-old clerk several times knocking him to the ground and then kicks him after he's already unconscious.

Cato -- then walks out, gets into the passenger side of a light colored sedan and drives off.

Moments before, the driver of that sedan, a woman is seen in this surveillance video chatting and laughing with the clerk as she buys some beer.

At 4:30 Friday afternoon... Cato and the woman were spotted leaving Wal-Mart by North Coastal Station deputies after recognizing them from this crime stoppers video.

The deputies pulled them over and confirmed they were same people from the surveillance video.

Cato's been booked into the Vista detention facility.

Detectives questioned the woman and released her.

They say neither the woman nor Cato would answer any questions leading them to a motive for such a brutal attack on a complete stranger.

Detective Reynaldo Dominguez said, "He suffering bruising and swelling to his head and face. He had a cut on the back of his head that required staples and there was some bleeding on his skull on the left side of his brain."