Police are beginning to piece together a profile of Tim Kretschmer the 17-year-old who went on a three-hour killing spree that left 15 dead before turning the gun on himself.Described as a loner with a fondness for weapons and combat computer games Kretschmer spent the early hours of Wednesday in an internet chatroom where the teenager warned of the massacre to come. “I’ve had enough of this stupid life,” he wrote. “It’s always the same thing, everyone makes fun of me. Nobody recognises my potential. I’m serious and I’ve got arms and tomorrow morning I will go to my old school and I will have a real barbecue. Maybe I’ll get out alive. Watch this space, you will hear more about this. Make a note of the place – Winnenden.” Schools closed for the day in Winnenden as students streamed to the Albertville School, where eight teenage girls, three female teachers and a male student were shot in the head at close range.