DS constant Vicious scratching/pinching

So DS2 is 16 months and is constancy grabbing all of our faces and scratching/ gouging out skin!!
Poor DS1 3 yrs, cops most of it! He takes it most of the time but he has enough of it and starts to get really emotional.
This afternoon was the worst though!
He scratched DS1's nose and under his eye so bad it just kept bleeding!

Then he would just laugh or give these strange faces. some were quite evil too!
He gets all kind of twitchy then starts with the hitting , pinching, then face grabbing gouging!

I am lost as to how this started or what to do to stop it! He is such a chilled out lil dude the rest of the time.

Could it be caused from having a big brother who steals all his toys etc? So he feels he has to get attention or payback?

How do I stop this??

Its very common, trust me. Its usually just seeing how much he can get away with.
If he does it to you while holding him, put him down & tell him NO scratching hurts & walk away from him.

If he does it to your 3yr old, you need to do the same, tell him no & turn your back to him & ask if your 3yr is ok. Avoid too much attention going to the behaviour. Negative or positive it is still attention that he will learn the scratching gets. So best to just say No firmly & then either walk away or turn your attention to your 3yr old & ask he is ok etc.

If it gets too much then I don't see a problem in taking his hands & placing them by his side while saying NO SCRATCHING & maybe even taking him to sit by the wall or something.

Good luck with it. Its one of those things that they do eventually stop doing though.