No need to speculate on heights or what was going on. Tom hit the nail squarely on the head when he said "guns don't just go off."
Someone screwed up big time!
True. But no evidence we have heard that points to foul play.
If she was on her knees in front of him as someone posted, the likely place for her to place her hands would be on his hips...and she might not have been paying attention to what she was doing...
I'll go with they were trying to "cover up" an embarrassing situation for the deceased and non-malicious negligence for the officer or both of them.
Until more evidence showing otherwise is presented.