I am under the impression that you can shoot trespassers on your property while in Texas.
As TexasRifleman said quite well, no. Absolutely not.
I won't ask where you got that erroneous impression. What is important is that
everyone understand his or her state laws before doing something stupid and illegal when encountering a trespasser.
In most states, the lawful thing to do when encountering a trespasser is to ask him to leave. In some states, if the trespasser refuses to leave, one's only recourse is to notify the authorities. And in some states, what the authorities will do is issue a citation, while in others, they may be empowered to make an arrest.
"Holding" a trespasser is unlawful in most places; after all, the trespasser is where he should not be, and keeping him from leaving is inconsistent with the intent of the law. It also can create a lot of legal risk for the property owner.
These things vary greatly by state, and within states, there are different kinds of trespass.
Before anyone ventures out with a gun to deal with a trespasser, he darn well better know what he can and cannot lawfully do in his state. I personally would not rely on applying dictionary definitions to the wording in the statutes without having a legal opinion based on the laws in the context of the rest of the code and on legal precedent. And I wouldn't rely on verbal advice from the sheriff. I've heard altogether too many people say "a policeman once told me...".
These "ranchers" in Texas obviously didn't have a clue.
No, shooting trespassers isn't legal in Texas, as these people will find out, and it isn't legal anywhere else in this country, for that matter.
Do not rely on any of the above as legal advice. Seek your own. But please don't anyone do anything stupid. It won't help the rest of us at all.