Griffin's parents are killed offscreen. We see sand falling on his mother's eyes.
The sandman has holes in his mouth. It is implied that his dad abused him and sewed his mouth together.
That's stated, not implied, then shown in a flashback.
The sandman kills many people but very little or no gore.
The only gory part which you may have to keep an eye on is a man points a gun at the sandman and the sandman melts his face offscreen. We then see the man falling and we see his skull covered in flesh.