In Hercules v. Gunther, 13 Va. App. 357, 412 S.E.2d 185 (1991), a power plant truck driver was delivering rocket propellant to a building. As he walked toward the building, it exploded. Although he sustained only minor physical injuries, two of his friends, with whom he had just been talking, were killed. Thereafter, he was diagnosed with PTSD. Affirming the commission's award, we held that the driver's PTSD was compensable as an injury by accident because it resulted from "an obvious sudden shock or fright arising in the course of employment." Hercules, 13 Va. App. at 362-63, 412 S.E.2d at 188.