UPDATE:
***UPDATE*** Des Moines Police Chief Michael McTaggart called the incident a “serious mistake,” and said the officer seen in the video was not at fault; the rifle had been left on the vehicle by the officer who used the car earlier.
“At shift change, an officer was offloading his equipment, set his rifle on top of the car, and then left and left that rifle there. Next officer came in, checked that car out, and didn't see the rifle on the roof and drove away,” said Sgt. Paul Parizek, the department’s public information officer. “I think we've all had a situation in our lives when we've misplaced something, we're looking for it. We walk by it two or three different times. That might help explain it. But it definitely does not excuse what happened.”