Life goes on. You comfort the wounded, including the emotionally wounded, especially those immediately around you. You do your best to meet your own needs and take care of yourself in healthy ways.
Your life can go on from this point, without harm, shame, or problem. There can be real and absolute problems that come from this event (possible retaliation from the friends/family/criminal contacts of the stabbing victim come to mind), but depending on exactly what happened, you and yours may be safe from that. If you are not, take -immediate- steps to protect yourself and those you love.
In recent years there have been over 120,000 aggravated assaults (that's a crime where 'injuring the other person' was considered to be the primary goal in the crime - not rape or robbery, and not successful murder attempts either) within the United States each year - here's some statistics from the FBI website to back that up if anyone wonders where that number came from -
http://www.fbi.gov/about-us/cjis/ucr/crime-in-the-u.s/2012/crime-in-the-u.s.-2012/tables/15tabledatadecpdfWhy does that matter? You're not alone by any means. These crimes happen, people who do them have family members, these family members must heal, deal with the problems and their own emotional pain, and survive and continue their lives.
I would strongly consider reminding my mother that she has me, that I love her, that she can only control herself, that she has set a good example (err, if that's false.. skip that part, but if it's true definitely include it) and that it is not her fault. And I'd tell the same to any other family members (other than the stabber) who were hurting. I'd be there for them, spend time with them, and help them see the better things in life that still exist.
It's often a shock when things like this happen. Just take extra good care of yourself and remember that it's not your crime. You didn't make it happen, you didn't decide it should happen, and you too are only responsible for yourself and your own choices.