Update 3:45 p.m.: Fairfax County police said the beaver tested positive for the Rabies virus.

Original Post: A beaver attacked an 83-year-old woman as she swam in Lake Barcroft in the Bailey’s Crossroads area Tuesday evening, causing serious injuries, Fairfax County police said

The animal bit the woman on multiple parts of her body, but she managed to make it to shore, where a witness stunned the animal by thrashing it repeatedly with a three-foot branch, police said.

The woman was transported to a hospital with non-life threatening injuries, and animal control officers euthanized the beaver, police said.

The attack occurred around 6 p.m. at the private lake, which is a popular recreation spot for area residents. It is surrounded by homes.

Authorities are awaiting the results of a rabies test on the beaver.

“At this point we have no idea why this occurred,” said Lucy Caldwell, a Fairfax County police spokeswoman. “There are a number of scenarios. Rabid is one scenario. Also, for example, if someone were to step on the beaver or were too close to its den. They are wild animals.”

Caldwell said beaver attacks are rare in Fairfax County.

The man who hit the beaver with the stick had been fishing at the lake. Caldwell said the man had seen it earlier in the evening, and it appeared to be acting normally.