You're too late

There was a murder on my street. A man walking his dog got shot about one block of where I live. It happened on Saturday night and since then I live in the safest street in DC.
We have about 10 police cars parked in the street, several giant flood lights and a truck equipped with cameras. I asked one of the policeman. "So why are doing this?". He looked surprised "To prevent any crimes. Criminals won't attack with that much light around". Maybe I am missing some important information in crime enforcement but it seems that the best use of 10 police cars is not in the street after a crime has been committed. I will fell much safer with these police cars going around in the complete neighborhood, not just parked in my street. The murderer is not going to come back to see how everyone is doing. He's gone. Somewhere in the city. Walking some other streets where there will be soon 10 police cars stationed and giant flood lights.
Always fighting the last war...