A police raid from the air?

This afternoon at work, we suddenly heard the sound of a helicopter flying low. We heard it getting closer and closer, then we saw it flying low again and again over the small business park where we are. It looked like a police helicopter, but we could not be certain. It would make sense if it was. To what purpose did it circle ominously above our heads, I have no idea. No siren was heard during or after, it was just this helicopter flying low and buzzing like a clunky metallic mosquito. I have to say, I found the whole thing quite exciting, if its dénouement or lack of was anticlimactic. This is the kind of stuff I read about in crime news. I know that police helicopters can be used for surveillance exercises, but they can also be prominent in major raids, drug busts and anti-terrorist operations, things like that. This is creative material for crime fiction. So I will try to remember this little episode for future use.