Heartbroken for Manchester

This morning we all woke up to the devestating news that a suicide bomber let off a bomb at Manchester Arena in the foyer as a pop concert finished. 

22 people were killed during the attack, some of them children. I feel so sick that this has happened. No one should go to a concert and never come home. 

This is a parents absolute worst nightmare. I'm holding my baby a bit tighter today. I fear for my daughter and the world that she is going to grow up in. Heartbroken. 

If these terrorists are know and are on a watch list, why aren't we getting rid of them? What is it going to take for action to be taken against these vile humans?

I just don't understand...