Police Presence Once Again

I was getting ready to go out just after 3:00pm today when I noticed a police car down the street. Well, thats not exactly true. I was getting ready to go out when I heard some noise out my window. I looked out the window and down the street a bit and saw a police officer standing on the boulevard with someone pinned on the ground. The gentleman was hand cuffed and leaned against the police car. Soon after, a second car arrived and the gentleman was placed in the back of the car.
When I left, I drove down the street, past the police cars and to the corner. I then saw another officer coming from the back lane.
Later, when I got home, I was told there were a total of four police cars that showed up for the incident.
I noticed the person who was handcuffed earlier on in the day. It must have been within half an hour of him being handcuffed. He was walking down the road pushing a stroller with a young child. I remembered him, because he looked very un-natural pushing the stroller. The whole way he was pushing the stroller looked odd.
I sure would like to know why the police are on my street all the time. I would like to know if these issues are domestic, or gang related. I would like to know if it is more of the same issue all the time, or if they are all isolated incidences.

The last time that I saw the police on my street was on Thursday. I was just coming home in the evening, and they were at the end of the street with their lights on. It looked like they were arresting someone.