There's only three ways this can have gone down, after thinking about it.
Scenario #1: He left his firearm unattended in the backseat with his kid (still in the holster since he's going after that manufacturer), and the child pulled the trigger. That means he left a loaded pistol with one in the pipe unattended and within reach of a toddler. Conclusion: He's a negligent douche who should have never been graduated out any police academy, nevermind have been allowed to carry a firearm.
Scenario #2: The pistol is on his person in a hip holster, and he allowed a toddler to access and discharge his pistol. Conclusion: See conclusion to scenario #1. He put his firearm within reaching distance of his kid, allowing the child to get his curious fingers inside of the trigger guard. Really? You're carrying while taking care of your kid and you wear a rig that doesn't adequately cover the trigger guard? He's lucky it didn't catch on any available foreign object and hit his child. Let's say he was wearing a back holster, though it's a little less likely because of the added cover a seatback would give against access and the fact that a 21 will never be mistaken as a compact carry pistol. But let's say that was the case... he's wearing it in a placement that's harder for him to guard against a grab, just above eye level to a toddler, with open access to the trigger. An open trigger holster is the only way this could possibly happen IMO since a three year old is going to have one hell of a time gaining possession of, drawing, pointing, and firing over two pounds of pistol at a trained LEO. Wearing an open trigger holster around a child is stupid. Doing so with a pistol that has the safety located in the trigger is incomprehensible.
Scenario #3: The story isn't completely true, and he's attempting to ride that version to the bank. Maybe this is a bit of a stretch, but the level of immorality some people will stoop to can never be taken out of any equation.
Then again it's pretty likely I'm just so jaded that I always expect people to be total morons.