In what was nearly a literal "eleventh hour" reprieve, Perry granted life to Foster on the day he was scheduled to be Texas' 403 execution since 1982. Foster had been tried jointly with the man who actually pulled the trigger in this murder. Foster's only crime was driving the car. The murder was not premeditated, rather it occurred after an altercation arose. The victim was shot approximately 80 feet away from the car. Since the convicted murderer has already been executed, this would have been a miscarriage of even "an eye for an eye" justice by taking two lives for one.
You can read more about Kenneth Foster (who will obviously remain an activist while in prison) here and you can see the Governor's statement here