The Beech B100 King Air aircraft operated by Island Express Air, was conducting flight 640 from Abbotsford, British Columbia, Canada to San Bernardino, California, USA with one pilot and 9 passengers on board. Weather conditions at Abbotsford at the time of departure consisted of a temperature of -2øC in moderate to heavy snowfall with winds of approximately 10 knots. Prior to the departure, the fuel tanks were filled to capacity and the pilot and passengers boarded the aircraft inside the operator’s heated hangar. The aircraft was towed outside of the hangar without being treated with anti-ice fluid, and taxied for the departure on runway 07. Due to an inbound arrival at Abbotsford, C-GIAE was delayed for departure. Once cleared for takeoff, the aircraft had been exposed to snow and freezing conditions for approximately 13 minutes. Approximately 4 to 5 seconds after takeoff, the pilot selected the landing gear control to the up position. As the gear retracted, the aircraft rolled approximately 30ø to the left. To correct the uncommanded left bank, the pilot applied right aileron, and the aircraft returned to a near wings-level attitude. In order to make an immediate off-field emergency landing, the pilot retarded the power levers and then applied forward pressure on the control column to land the aircraft. The aircraft struck terrain between runway 07 and taxiway C. The aircraft slid across the snow-covered ground for approximately 760 feet before coming to rest in a raspberry patch located on the airport property. Four passengers and the pilot sustained serious injuries as a result of the accident which destroyed the aircraft. Findings as to causes and contributing factors: 1. The occurrence aircraft exited a warm hangar and was exposed to 14 minutes of heavy snow in below-freezing conditions. This resulted in a condition highly conducive to severe ground icing. 2. As the aircraft climbed out of ground effect on takeoff, it experienced an aerodynamic stall as a result of wing contamination. 3. The pilot’s decision making was affected by continuation bias, which resulted in the pilot attempting a takeoff with an aircraft contaminated with ice and snow adhering to its critical surfaces. 4. The pilot and the passenger seated in the right-hand crew seat were not wearing the available shoulder harnesses. As a result, they sustained serious head injuries during the impact sequence. 5. During the impact sequence, the cargo restraint system used to secure the baggage in the rear baggage compartment failed, causing some of the baggage to injure passengers seated in the rear of the aircraft cabin.