He was 91, and in addition to probably being the most ubiquitous voice artist ever, was also a WWII vet and a very generous, civic-minded fellow.
I remember hearing his voice in a filmstrip, when I was a very young kid. The story concerned an Indian legend about a guy who turns into a snake and his legs fused into a tail. His narration creeped the bejesus out of me.
Here’s his obituary.
I first remember hearing that voice on the Discovery Channel’s “Movie Magic,” circa 1994. 
Rest easy, friend.
Fortunately, no foul play is suspected.
RIP. 
Thanks for linking that obituary, Nonsuch. Clearly Thomas was a member of the Greatest Generation, and he’s left quite a legacy.
Thanks for posting this. Peter Thomas was the greatest voiceover artist of all time (IMHO, of course, though I suspect there are others who would agree).
I always said that if I had his voice, I’d rule the world. Fortunately, he used his powers for good.
That’s so sad. Although making it to 91 is a good long run for anyone.
I never knew the man’s name, but his voice was immediately recognizable. Crime shows will never be the same.
If anyone else is like me, trying to remember ***exactly ***which ubiquitous voice-over narrator he was, this was him…