Did you see there are other people in the restaurant? Customers + staff. Maybe 10-15 people. Some are cowering under their tables in fear as they believe their lives are in danger.
Why is your primary concern with the criminal who voluntarily instigated this situation?
My concern is the vigilante tomorrow that decides to stake out the local school, hospital, church, deli, bank, gas* station, cinema, gym, abortion clinic, or otherwise. Untrained, inexperienced have a go heroes eventually goes wrong. And who ends up accountable?
My problem here is escalation. The killer gets off, so anyone desperate or stupid or high or deranged enough next time goes in fully loaded, then its bloodbath time 'cos "everyone wants to stop me"....
Hypocrisy remember...