Happens all the time, everyday, all across the United States.
Please see: The Police State Murder of David Woodman
As for this particular case, I don't believe the cover-up cops version. The whole explanation smells fishy.
"Mass. DA says police justified in fatal shooting
Prosecutors have concluded that the Mansfield officers who fatally shot a 20-year-old man in April were justified in their actions. The Bristol County District Attorney's Office said Tuesday that the officers' actions in shooting David Semenza of Easton were necessary to defend themselves. Semenza was a passenger in a Ford Explorer driven by another man when they allegedly robbed a Mansfield bank on April 24. Customers alerted police, who pulled over the vehicle. District Attorney Sam Sutter said officers used "reasonable force" after Semenza "willfully and intentionally" refused to comply with police orders to get down on the ground, moved toward them and removed a black object from his pocket, which police believed was a gun. The black object turned out to be a cell phone (AP)."
Killed over an ALLEGATION, huh?
And do you believe that horse shit story the cops put out?
Also see: They Always Get Their Man
Drunk Killed in Downtown Boston and Other Unsolved Crimes