What are they waiting for? Their croissants to bake?
Go in there and get that piece of dirt the hell out of that rats nest he is living in. You have guns, use them.
The building is evacuated, smoke him out. Flash bang him.
Maybe this is just a European thing. Be very polite to the mass killer and threaten him with loud bangs to let him know you mean business.
When he dropped a gun out of a window in exchange for a radio to talk with police, they should have taken him out there.
How many more firecrackers are they going to throw into his window before he comes running out and mows down the French police waiting on him with a cannon?
He has already admitted guilt! VOILA! Time to lock and load.