Question about someone who's unstable?

Ok, so first off I live in a ghetto neighborhood, there's a total of 8 apartments where I live (including myself) and out of those 8 there are about 3 other decent neighbors and 4 that are totally ghetto.

Most apartments are like 2 bedroom 1 bath each. One of the ghetto houses has a "family" with a dad that is about 30 yrs old, his 30 yr old girlfriend, their 2 kids, 2 kids from the dad's prior relationship where the previous mother took her own life, and the dad's mother who is 53, tatooed up.

The dad's mother is very unstable. Since my mom complained to her son that his kid was throwing rocks at our window, the she won't let it down. Another neighbor has complained that their music was too loud. I don't know how she is with other peoples houses, but she seems to have of a fixation on our house. Now recently she pulled a gun on her son, I don't know the whole story. Now how do you deal with this grandmother when everytime me or one of my friends or my mom steps outside our door and she leers?