Death penalty even though he didn't commit murder

The defendant Kenneth Foster was driving a car with three passengers in it. One of them, Mauriceo Brown, left the car and got into an altercation with Michael LaHood and ended up shooting him dead. Brown has been executed. In Texas, they can apply the law of parties to capital cases (the only state to do so) -- being an accomplice makes one the same as the principal. Brown claimed to the end that it wasn't planned and there seems to be evidence unheard at trial to support this assertion.