Russell Rios was being pursued by loss prevention workers at Walmart when off-duty Sgt. Jason Blackwelder joined in the pursuit.
According to the lawsuit, Rios ran into a wooded area near the store with Blackwelder chasing him. Moment later, Rios was fatally shot.
Conroe police initially said that Rios was fighting with Blackwelder and choking him, which implied self-defense.
Blackwelder was indicted in September by a Montgomery County grand jury on a charge of manslaughter.
The suit was filed in federal court in Houston. The family's attorney, Ryan MacLeod of Beaumont, says that a forensic exam shows Rios was shot in the back of the head.
The suit is asking for unspecified damages. But most of all, the attorney says, the Rios family wants answers about the teenager's death. Rios had just gotten a part-time job as a bank teller and was a student at Lone Star College.
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