Santillan told investigators on June 30 he was trying to sell his game system to Patino, who took him for a drive, along with two other men in their 20s.
Santillan told police that at 3rd Street, south of Yucaipa Blvd., Patino pulled a silver-colored revolver and pointed it at the victim's head. Another man in the vehicle pulled a knife and held it against the victim's body.
Patino ordered Santillan to hand over the game system and threatened to kill him.
Santillan was punched twice in the head, robbed of other personal property and ordered out of the suspect's vehicle.
A search warrant at Patino's home in Banning turned up a weapon and most of the items reported stolen.
Patino remains at large.
An arrest warrant has been issued for Patino, 21, who is described as 5 feet 8 inches tall, weighing about 160 pounds.
Anyone with information about Patino and the two other males is asked to call the San Bernardino Sheriff's Department at (909) 790-3105.