Milwaukee police say three parking checkers with the Department of Public Works have been targeted by shooters this week.  A 25-year-old man was arrested when he fired a shot at a parking checker while she was putting a ticket on his car early Wednesday morning.  She wasn’t injured in the 3:00 a-m incident.  The first shooting happened shortly before 5:00 a-m Tuesday when two parking checkers spotted two people trying to break into a car.  When they started following the suspect vehicle, shots were fired — though nobody was hit.