Bicycle detail

I locked up my bike with a Kryptonite U-lock in front of Tupper Hall on Tuesday December 15th at around 11:30am. I went inside Tupper for work and did not exit until around 3:00pm.
Upon exiting, I saw that my bike had been stolen, with only my bike helmet and the snipped U-lock remaining. A poor-condition silver Gary Fischer mountain bike also lay abandoned next to where my bike had been locked up. A witness approached me (a mid 30's man named Ryan who works in the Tupper building) and described how he has seen a thief clad in black clothing snip my lock with bolt cutters and flee on my stolen bike after Ryan yelled at him to stop. This interaction between Ryan and the thief occurred at around 2:30pm. Ryan also confirmed that the abandoned silver Gary Fischer bike was the bike thief's bike. Ryan was not able to determine any distinguishing features of the thief, except for the thief having a generally masculine build and being clad in black clothing. No other witnesses could be identified.
With no other witnesses around to talk to, I took possession of my helmet, the broken lock, and the thief's abandoned bike for use as potential evidence.