TexasCHLforum.com

It seems to me that the easier argument would be that the person entered the building to protect the lives of others and utilized reasonable and deadly force would be fairly well covered under §9.33, “Defense of Third Person”.

More specifically, §9.33 states,

“A person is justified in using force or deadly force against another to protect a third person if:

(1) under the circumstances as the actor reasonably believes them to be, the actor would be justified under Section 9.31 or 9.32 in using force or deadly force to protect himself against the unlawful force or unlawful deadly force he reasonably believes to be threatening the third person he seeks to protect; and

(2) the actor reasonably believes that his intervention is immediately necessary to protect the third person.

Then you can get into the chicken/egg argument about the validity of §46.03 “Places Weapons Prohibited”.