A very stern this is not how we act, one word directions on what he could say instead of screaming, explain that you can't understand the problem when he is screaming, stickers for being able to pull himself together quickly after redirection, hugs and praise when he is able to pull himself together.

Once he is able to pull himself together quickly with these directions up the anti by changing the expectations to not throwing tantrums in the first place.

Something happened to trigger this. You may never know but it is important to do some serious thinking and talking with the parents about any changes big or small that happened prior to the beginning of this behavior.

The parents need to be on board with this form of 'correction' too. consistency is key.

If ignoring the behavior isn't working after a few weeks of starting, more action is needed in order to correct the behaviour

Remember that this child is not even two yet so use language they can understand when redirecting. Also slow your speech down and lower your voice. Lower speech help calm children and slow speech helps understand (This can be impaired when children are REALLY upset)