The March shooting was the third accidental discharge because of gun-mounted flashlights documented by the Denver Police Department.
Perhaps there is another explanation - something akin to group-think. Office 1 has an accidental discharge. He thinks it is because of his flashlight. He may or not be correct about causation, but that's what he says. Gets some discipline, but not fired. Some time later, Officer 2 has an accidental discharge. He is now predisposed to thinking the flashlight is the problem. He is also probably convinced. Officer 3... well... you get the idea.
Note: this does not mean the flashlight issue doesn't exist. It certainly might. It just seems strange to have 1 department with 3 instances of an event that I haven't heard of from any other department.