Here's the story according to Prolly's Blog: A bike messenger locks his bike to meet his friends at a cafe. Same messenger comes out later to use phone and watches as a guy looking over his bike pulls out a cordless drill to drill out the u-lock of the watching messengers bike.
Below is the video how the messenger and friends reacted to the bike thief.
Please note that despite the fact that this guy was caught red handed attempting to steal a bike. The guys who caught him used a fair amount of restraint on their part. The bike thief was not bleeding or visibly injured. Just scarred to death and most likely, currently pursing the classifieds seeking a new line of work.