This event, if it occurred, is getting scant attention. From the Haitian Times:
A U.N.-Backed Police Force Carried Out A Massacre In Haiti. The Killings Have Been Almost Entirely Ignored.
The police officers were working with the United Nations Mission for Justice Support in Haiti. It was launched in October, a reboot of a previous mission that had begun in 2004, when thousands of U.N. troops were sent to Haiti following a coup d’etat, tasked in part with restoring stability and reinforcing national police capacities.
I don't have a good sense of the Haitian Times as source, hence the question: Did a UN Backed (loose affiliation or sponsored group would suffice as "UN Backed") perpetrate a massacre in Haiti?
Seems the Intercept might have been the original source, with the article dated Jan 2018, with the massacre being reported November 13, 2017.