San Diego police Sgt. Ray Battrick says the suspect on Saturday presented a note demanding money to a teller at the San Diego National Bank. He fled with an unknown amount of cash.
Battrick says it's unclear whether the suspect had a weapon.
The robber is described as a tall man in his 70s with white hair, a gray mustache and glasses. He was wearing a white beret, argyle sweater and brown sports jacket.
Battrick says the oxygen tank was in a black bag and connected to the man's nose with plastic tubing.