According to this report
on the Australian Broadcasting site, a student in Evora, Portugal parked his car in a public lot and took the plates off to have them straightened.
Someone saw him take the plates off and leave the car, so they called the police to investigate.
The police decided that this was typical "terrorist car-bomb behavior" and called the bomb squad.
The bomb squad decided that since they couldn't find a bomb to disarm, they had better blow up the car in a controlled fashion, which they then proceeded to do.
The student returned with his straightened plates as they were sweeping up the remains of his car.
Well, "the police blew up my homework" is certainly more original than "the dog ate it".