Police have arrested a 45-year-old man suspected of dousing a homeless victim with fuel and setting him on fire in an unprovoked attack caught on video.

Surveillance footage from Santa Ana, California showed the moment when a man was engulfed in flames and left for dead in early April.

He can be seen sitting on a sidewalk near the intersection of First Street and Broadway when a man rides into the frame on a bike, pours an accelerant over the man and sets him alight.

The suspect had covered his face and was dressed in black when he approached the man, who was alone in front of a closed business.

The victim, who tried to get away from the attacker, suffered first-, second- and third-degree burns to his upper body. Physicians at a local trauma/burn centre performed surgery on his wounds and he remained in a critical condition.

The Santa Ana Police Department said in a news release on Tuesday that Adrian Alberto Rodriguez Herrera, a 45-year-old transient, was arrested near the scene of the attack.

Officers who specialise in interacting with the homeless detained Mr Herrera and his bicycle after allegedly matching him with the description of the crime and surveillance footage.