MEXICO CITY (AP) — Relatives of nine U.S. dual citizens slaughtered in northern Mexico last month say President Andrés Manuel López Obrador prayed with them for the safety of the country and pledged to visit the region.

Julian LeBaron said Tuesday that during the Monday meeting at Mexico City’s National Palace, the president and his Cabinet assured him that “at least four” suspects have been detained in the Nov. 4 killings.

Three young mothers and six children were killed in the attack near the border of the northern states of Sonora and Chihuahua. Officials have said a drug cartel is suspected in the attack.

LeBaron said officials have confirmed to them that the killers filmed the attack themselves and set fire to an SUV in which one mother and her four children died.