Doctors Without Borders said on November 11 that one of its ambulances carrying three young men with gunshot wounds was stopped by Haitian law enforcement officers.
The men, who appear to have been supported by a paramilitary self-defense group, attacked the car, rescued two patients, took them out of the hospital and executed them.
Humanitarian groups condemned the violence in a strong statement last week, saying workers had been tear gassed and detained for hours against their will.
This incident appears to have been the last straw for Doctors Without Borders in Port-au-Prince, but it was not the only recent example of extreme attacks on staff, at least for the time being.
The announcement comes amid worsening violence in Haiti, with about 25 gang members killed in the capital on Tuesday.
Police said residents helped officers suppress an attempted attack in the suburb of Petionville.
In an effort to stop gang incursions, residents armed with machetes and makeshift weapons barricaded the streets and shut down the neighborhood.
