Saundra, that, sadly, is a distinct possibility.
I am assuming you mean that it would be Moslems taking revenge, but revenge against whom? Revenge against innocent New Zealanders, the people who welcomed them to their country and allowed them to freely follow their culture and religion.
Jacinda Ardern has said there will be changes to NZ's gun laws - already stricter than USA / Canada / Oz, but not as strict as the UK. However, there are an estimated 1.5 million 'registered' firearms in a population of about 5 million ~one for every three people. Nobody knows the total number of registered and unregistered firearms nor where they all are.
The prospect of tit-for-tat "revenges" is enormous.