Help me to find out my unsolved questions

Everyone knows there's a phrase

Everything Happens for a Good Reason

and now i have a big question ,that if everything happens for good..
then whats so good in this blasts which took place in Delhi,Jaipur,Bangalore,Ahmedabad.
All those who did this are not humans ? Why do they do this ? what they are going to get by killing innocent people.
1000 innocent people have died. whats their fault in this. why they have to pay for the mistake they have not made.

What Good in all this that had happen to the innocent people.

I tried to find out the answers for all this question but i was helpless as i couldn't find their answers.

Please help me to find me the answers of the questions.