Authorities say a swimmer at a Bavarian lake drowned a dog in self-defense after the animal bit his arm and wouldn't let go.

Police said Friday the 83-year-old owner was walking his dog alongside the lake in Schwarzenbach an der Saale when the German Shepherd attacked the 49-year-old on Monday night.

Police say onlookers tried to help pry the dog's jaws off the man's arm but were unable to free the appendage. That sent the swimmer back into the lake, where he plunged his arm — with the dog still latched on firmly — under the water.

The dog still didn't let go, and drowned.

The swimmer was taken to a hospital and treated for serious, but not life threatening injuries.

The owner is under investigation for negligent bodily harm.