Witnesses reported that the aircraft's engines sounded normal as the aircraft climbed at an unusually steep angle after takeoff to about 300 feet agl, then stalled, rolled to the left, and spun into a hangar. One witness reported that as the aircraft rolled over he could see that the nose baggage door on the right side of the nose was open and folded back in front of the windshield as the aircraft continued to roll. The pilot had 487 hours total flying time with 23 hours in multiengine aircraft. He had received an 8.6 hour checkout in the accident aircraft 2 weeks prior to the accident.