This could be any number of things, w/ so little information available. But what the heck...
***SPOILER***
...Towards the end of NIGHT FALLS ON MANHATTAN, James Gandolfini eats his service revolver. He's in his car, not in a bathroom stall. He is dark-haired, balding (or thinning), in his 30s-40s, though. It was a mainstream cop movie (co-starring Andy Garcia, Ian Holm, and Richard Dreyfuss) and it was downbeat........
can't be it because it was 100% in a public restroom...
but thanks for bumping this thread. I was thinking about this exact scene just the other day and I couldn't remember if I'd asked here or not