Changing a will

Recently, my great uncle passed away. He fell and broke his hip so for months he was in the hospital and rehab.

He had a pace maker put in and because of a hernia in his chest, he had trouble breathing and passed away at the age of 90.

My great uncle doesn’t have any kids or wife. He was extremely close to my mom and her 2 sisters and brother. He had the closest relationship to his nephew (mom’s brother) and he was his executor.

The day he died, the family found out the 2 nieces (moms sisters) changed the executor position to niece A and changed his will where he gives 4 guns and ammo to a 15 year old boy (niece A’s son). The new will was done days before his passing.

Some other men in the family were given guns along with niece A. No other women were mentioned in the will.

The family is now angry and confused. But the 2 nieces feel like they did nothing wrong. They claim he asked for his will to be changed and that he was “with it” - understood everything that was going on.

Who is right? Should they have changed everything?