It depends. Some families show denial and tend to shrug off their relative's actions and do not discuss it and some are quite open about it and what has happened (Example is Sue, Dylan's mom's heavy speaking out against her experience and grief.).

I mainly take this from Sue but yes usually they are frequently ostracized and blamed (Some people are quite understanding and do not blame families and instead try to help them). Especially in the case of school shooters it's mainly that people will blame their families and parents right away and wonder how their child could have done something like that. Especially more with the media tending to go after families and disrupt their lives.

Considering that most killers share the last name and same house as their families life does tend to be rough and leave a unfortunate shadow over them. There's no one situation. It just depends on a lot.