The people who did this will be arrested within a few days or weeks. I'd be extremely surprised if this were not so.
The only way the military will be involved is if the police hand control to the SAS because they've holed up somewhere.
If that happens, they'll all die.
I certainly hope so. Bless them and keep them in this hard time, Britons deserve justice. As hard as they try and as good as they are, increasingly police and judicial procedures seem to fall short.