What to Do if Your Roommate Threatens You With a Knife

My question involves criminal law for the state of: NJ

Last Saturday on 06/24/2017 my roommate who is acting and making stories like a Shaikh Chilli to pretend himself as very sharp fighter and a person having no humbleness, attacked me with a sharp knife and threats me to kill.
As we are living together in a three bedroom apartment (3 males) and joining the home work by turns or together. Ha asked me to make a tea for him and I replied that i will make but you have to clean the utensils in reply of which he showed his anger and became out of control.
I didn't call police because his brother is good friend of mine and I just kept quite.
He yelled and threat me continuously but i did not reply.

I just want to know what should I do in this type of situations.

That which you did not do: call the police. Perhaps finding a new place to live isn't far amiss either.

Call the police.

If you don't want to call the police then do nothing and wait until he stabs you to death.