VIDEO: The widow of a Utah firefighter who was killed when a supertanker dropped nearly 20,000 gallons of fire retardant near his position fighting a Northern California fire is suing Cal Fire and the aircraft company for alleged negligence. State investigators found 42-year-old battalion chief Matthew Burchett of Draper, Utah, died last August when fire retardant was dropped from an aircraft flying barely above the treetops because spotters mistakenly sent it on a route too close to the ground. The retardant struck with such force it uprooted an 87-foot (27-meter) tree that fell on Burchett. The Sacramento Bee reports that a lawsuit filed Wednesday by Burchett's widow and son says the firefighter was in a "safe zone" when the retardant was dropped. Cal Fire did not immediately comment on the lawsuit.