No there are no other options.
The shooter probably has a gas mask. He is not coming out of the building alive.
The remaining victims do not have masks and cannot leave their positions. Trapped in a confined space, they could die from a gas attack.
Do they know how many are left inside? Saw photos of several being evacuated - several in scrubs - some wrapped in blankets.
Well - tickle me with a feather. He surrendered!
Have a pleasant dinner tonight, Officers.