Missouri Executive Order 44 (eat your heart out, George) was signed by Lilburn Boggs on October 23, 1838, and ordered that Mormons in the state be “exterminated” or exiled. This destroyed Boggs’ political career, but the order wasn’t formally rescinded until 1976 as a goodwill gesture by Governor Kit Bond. Zombie laws and orders are a hell of a drug that I imagine keep lawyers up at night.
There was a show that came out a few years back called American Primeval that was about this time period and these people. I’m not sure if the show is meant to be this specific massacre, or a fictionalized version of events, but I thought it was super compelling.
https://en.wikipedia.org/wiki/American_Primeval