Surveillance video from a Sports Chalet in Torrance, Calif., shows Dorner entering the store with two small oxygen tanks and heading to the scuba section to get them refilled.
According to TMZ, who acquired the video, Dorner also purchased another, larger scuba tank and stopped to chat with a cashier before paying for the items with cash and leaving the store.
The video was captured between 9:21 p.m. and 9:38 p.m. on February first. The bodies of the first two victims, Monica Quan and her fiancee Keith Lawrence, were discovered in a parking lot at California State University-Fullerton around 9 p.m. on February 3. Quan was the daughter of retired Police Capt. Randy Quan, who was part of the review that led to Dorner's dismissal from the force in 2009.
Law enforcement sources confirmed to TMZ that the man in the video is Dorner.
Dorner, who was a member of the U.S. Naval Reserve underwater unit and is a trained marksman, attempted to steal a boat near San Diego on February 6 in an apparent attempt to flee to Mexico. When a rope got tangled with the boat's propeller, he fled the marina.
Dorner then allegedly killed a Riverside police officer and wounded another on February 7 before going on the run. He left detailed writings alleging widespread corruption and abuse against minorities by his former Los Angeles Police Department colleagues.