I only lived in TX for a few years but yes I think they can.
Wow...so lets assume these WalMart guys thought the dude had stolen something....they tackled and killed him...and he turned out to have nothing...or a receipt for whatever it was they saw.
It seems there is a bit of a policy problem here.
The way things are, if I'm walking through Walmart and just happen to stick my hands in my pockets, or, as actually happens to me quite often, I buy some fishing line and the beepers go off at the door, Chuck in housewares has the right and duty to kick my a$$?