Was there anything special about your bike or what you were carrying/wearing? Were there other cyclists in the area? Was it unusual to see a cyclist at that time of the day? In other words, wonder if they were targeting anyone on a bike, or especially you.
I was just riding my winter bike which I guess looks pretty nice to a bike thief. I honestly think they saw me as an easy target and they probably became pissed off when I turned out not to be. I see at least three other year round regular bike commuters that travel the area this occurred a couple times a week around the same time. So its very possible they were targeting cyclist.
I wear Gore bike wear gear for winter commuting and a black balaclava. Also here is how my winter bike is setup.