Black beetle

On my way for a walk with a friend, we found on our path several black beetles also walking there.
One was just trying to go on the wings and you could see movement in the underwings, like a kind of trembling.
A moment later he was gone.
A little further there was one lying on his back...not alive anymore.
His colours were briljant from deep purple ultramarine blues and deep magenta.
later I found out his name:
Dung-beetle, Mestkever or Geotrupidae.