Regular police are not allowed to carry firearms in Great Britain. They have, as you said, 'specialists' for that, and even the specialists have strict protocal to follow.. Gun control is pretty strict in Britain. I'm surprised you didn't see the Alex Jones/Piers Morgan debate on gun control. I believe Piers mentions this.
If you're not sure about facts, it's easy to look up.
The perpetrators are still alive. If they had been killed, tell me you wouldn't have said the "London police were 'shutting them up'". It doesn't matter what happens, it's always twisted as a false flag or some conspiracy of some sort.