Authorities are investigating why an off-duty FBI agent opened fire from the window of his Queens home at three men he believed were breaking into his car, sources said.

The agent apparently fired from a second-floor window of his South Ozone Park house at the men, shortly after 5 a.m. Wednesday. One of the men was struck, and all three fled, police said.

It is not clear why the FBI agent fired shots at the men, who may have been trying to steal a radio from the car, which he and his wife own. His wife was inside the house at the time, sources said.

Police began searching local hospitals. A wounded man at Brookdale Hospital, who is being questioned. He had been shot in the lower back and is expected to survive.

Police continue to search for the other two men. No gun was recovered at the scene.

A spokeswoman for the Queens district attorney's office said the matter is under investigation.

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