Just so that everybody is aware what I just witnessed, my car almost got broken into. Luckily, I was looking out the window and saw him walking up to the car, hands in his pocket, nonchalantly looking into the windows to see what was inside. When I cleared my throat so that he heard I was watching him he immediately turned his face away, and started jogging slowly down the block, crossing the street twice, zigzagging.
This was on Randolph Place NW, and then he left to turn south on first. I notified the police, but here is the description for everyone's benefit: black male, approximately 40 years old, give or take five years, I believe he had a mustache, shortly cropped hair, professional-looking throughout, no baggy pants, just professional black slacks, regular black shoes, and a dark brown jacket that looked to be leather or suede.
Just be aware, and if you see people casing cars or houses, call the police. The officer was on the block within literally 60 seconds, very impressive!