Tragic.
Firearm safety is paramount.
Sadly,, in my experiences,, only about 15% of LEO's are active gun people,, and as such,, the other 85% are not as well trained or safety conscious.
My LEO son has regaled me with several discussions of how MANY of his fellow officers can barely pass the annual qualification. His experiences mirror what a brother from another mother, former Federal agent shared with me. Any my brother was a firearms instructor for part of his career.
They may call it an accident,, but I beg to challenge that description. I'd call it a "negligence" event.