San Francisco police are still trying to determine why a UPS driver shot and killed three co-workers before turning the gun on himself at a package sorting and delivery center, but he had filed a workplace grievance. The 38-year-old shooter was wearing his uniform when he entered the location and opened fire. The later discovered workplace grievance complained of excessive overtime. The San Francisco attack comes nine days after another workplace shooting left five people dead in Orlando, where a former employee armed with a semiautomatic handgun and a hunting knife opened fire at an awning manufacturer and killed five.
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