Issue of qualified immunity for a police officer is for trial, since the use of deadly force against an armed individual in a volatile situation is unconstitutional absent proof of threat to others.
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Not written by a barrister. The name was thought up by a second-year American law student sitting in a coffeehouse in Manhattan. Neither an authoritative statement of the law nor legal advice.
Don't rely. Quick work.