Mrs.Radley was screaming around her house screaming, "Save us all!" or something like that because her son, Boo Arthur Radley drove scissors into his father's leg and continued to do his activity. Why did she scream?

Arthur drove scissors into his father's leg.

Because Boo doesn't socialize, he is in his house, probably feeling miserable about himself because believe it or not, his father and brother have taken his life away completely. The description you addressed above connects to having Mr. Radley's life taken away. Boo was not a fairly well behaved child when he was young, so don't think he drove scissors into his father's leg on purpose.

Agreed Megan! Boo loves the children, that's why he leaves gifts in the knothole tree.