Two wounded patients were killed after police officers and vigilantes attacked an ambulance in Haiti, humanitarian group Doctors Without Borders said on Wednesday.

The alleged executions in the capital Port-au-Prince are the latest reported act of heinous violence in the restive Caribbean nation, which has been plagued for years by rampant gang warfare and political turmoil.

Doctors Without Borders, also known as Médecins Sans Frontières (MSF), said law enforcement officers stopped one of its ambulances as it was transporting three young people with gunshot wounds to an MSF hospital in the Haitian capital on Monday.

Police then diverted the vehicle to a public hospital, where officers and members of a vigilante group “surrounded the ambulance, slashed the tires, and tear-gassed MSF staff inside the vehicle to force them out,” the organization said in a statement.

The officers and vigilantes then took the three wounded patients outside the hospital grounds and at least two of them were killed, MSF said.

The third patient was not killed, Garnier said. Authorities suspected the patients of being gang members, but MSF had no information to support that claim, he added. Garnier also said the officers were wearing protective gear but it’s unclear what police unit or agency they belonged to.

MSF condemned the attack, saying its staff were threatened with death and held against their will for more than four hours before being allowed to leave.

“This act is a shocking display of violence, both for the patients and for MSF medical personnel, and it seriously calls into question MSF’s ability to continue delivering essential care to the Haitian people, which is in dire need,” Garnier said.

MSF is organizing a high-level meeting with Haitian police to address the matter, he added.

This is the latest deadly ambulance attack that MSF has reported in Haiti. In December last year, the organization said armed men stopped an MSF ambulance, dragged a patient out and killed him.

The MSF report comes just two days after three US-based planes were struck by gunfire in Port-au-Prince, forcing the suspension of flights and closure of the city’s international airport.

Haiti’s transitional presidential council blamed armed gangs for the gunfire that struck one of the flights, accusing them of aiming “to isolate our country on the international stage.” The plane shootings happened on the same day the council swore in a new prime minister, businessman Alix Didier Fils-Aimé, who pledged to restore democracy and security in the country.