Poll: What is this noise?

People with actual firearm experience, what is the sound at the end of this security camera video? This happened on 4/22/10 at 12:58 a.m I cannot confirm the vehicle was the source of the sound, but I do suspect it.

This occurred on 51st Terrace N in St Petersburg 33709. The sheriff department did show up and search for a cause shortly after.

Видео Poll: What is this noise? канала Squanto Productions