At the end of the movie, when Sigourney Weaver is at the roof, daring the killer to shoot her, the killer is shot in behind by the female cop. An overhead scene shows the killer dropping to the ground, his gun hand hitting a beam. As Sigourney crosses the roof, she kicks the gun out of his hand in the GRAVEL.

I'm not certain, but 1 of two things happened.

1. Either the gun changed hands

or

2. The body rotated 180 degrees, like the doughnuts.