A helicopter in the night

I heard it, but did not see it this evening, around 8:00. The sound of the rotor of a helicopter, flying at low altitude. It was somewhat menacing and ominous, as such sound often is. I wonder why there was one flying low around here. We were once woken up by one in the middle of the night, a couple of years. Turned up it was the police looking for burglars on the run. Maybe this is the case for the one tonight as there has been burglaries around here recently. Maybe I am just a bit paranoid and have a vivid imagination. All the same, it was quite dramatic.