You're comparing very different situations: in Norway, once the killer was arrested the risk of further damage was low. In the UK, there might be further riots.
If you are dealing with a crisis, I think you should do things more or less in this order, and I don't think we'll be ready to start on #4 for another day or two in the UK:
1) Don't make it any worse.
2) Prevent further damage from happening.
3) Clean up the existing damage.
4) Investigate ways to prevent a repeat occurrence, and implement if a good solution is found.
If you are dealing with a crisis, I think you should do things more or less in this order, and I don't think we'll be ready to start on #4 for another day or two in the UK:
1) Don't make it any worse.
2) Prevent further damage from happening.
3) Clean up the existing damage.
4) Investigate ways to prevent a repeat occurrence, and implement if a good solution is found.