Sorry to gear about your tragedy, but like so many have said God is not done with you and I do not know your religous beliefs, but you are in God's hands and while we sometimes do not under stand the why of how did this happen to me, he has shown you his mercy, even in the storms we must still praise him.
It is easy for us to blame an elderly lady and maybe rightfullys so, but I am sure her life has been changed by this tragedy as well, she too is a victim and we do not know the pain or suffering she may be enduring, so my prayers are for your family your friends and the elderly lady,while your lives will be changed I pray for forgiveness and healing of body and mind for all that have been touched by this tragedy.
I am sure you are dealing with the issues and hurts of your situtation.
One of my favorite Christian groups is Casting Crowns, they have a song that I am reminded of every time I pass through a storm in my life, here are the words if you do not mind me posting them here, may God Bless all of you,
Praise You In This Storm" -Casting Crowns
I was sure by now
God You would have reached down
And wiped our tears away
Stepped in and saved the day
But once again, I say "Amen", and it's still raining
As the thunder rolls
I barely hear Your whisper through the rain
"I'm with you"
And as Your mercy falls
I raise my hands and praise the God who gives
And takes away
And I'll praise You in this storm
And I will lift my hands
For You are who You are
No matter where I am
And every tear I've cried
You hold in Your hand
You never left my side
And though my heart is torn
I will praise You in this storm
I remember when
I stumbled in the wind
You heard my cry to you
And you raised me up again
My strength is almost gone
How can I carry on
If I can't find You
But as the thunder rolls
I barely hear You whisper through the rain
"I'm with you"
And as Your mercy falls
I raise my hands and praise the God who gives
And takes away
I lift my eyes unto the hills
Where does my help come from?
My help comes from the Lord
The Maker of Heaven and Earth