If a locksmith changes my locks and I am not home and a stranger walks in the house could the police arrest?

The locks at my brother house was change and while locksmith changes the back door a mean neighbor walks in the front door and takes stuff and pictures and the locksmith told the guy to get out. He wasn't allowed in the house. Could the police arrest him? Hometown police in Illinois said no. The neighbor said the locksmith said he could go inside, but that is a lie. He keeps harrasing my brother and my brother is going to move in 5 days.