Several individuals wearing uniforms fired the shots that killed three Federal Police officers at Mexico City's Benito Juarez International Airport on Monday, airport security officials told Efe.
Two of the officers were pronounced dead at the scene and the third died while being treated at a hospital, the Public Safety Secretariat said.
It is not clear what police agency or military unit the shooters belonged to, but one of the dead officers had been investigating a corruption network involving the Federal Police and organized crime groups, airport security officials said.
Both the assailants and the victims were wearing Federal Police uniforms, and the dead officers did not even have a chance to draw their weapons, eyewitness Paula Lopez told Efe.
The shooting occurred around 8:50 a.m. in the airport's Terminal 2, which handles Aeromexico flights, sending terrified travelers scrambling for cover.
The three Federal Police officers were on patrol in a hallway when they encountered several subjects wearing uniforms and engaged them in a brief argument, airport security officials said.
One of the officers was knocked to the ground and shot at point-blank range, while the other two were shot as the assailants tried to flee, airport security officials said.
Officials have not said whether any arrests have been made in connection with the shooting.
The Federal Police has been investigating a possible police corruption network for more than three months, working with other law enforcement agencies that operate at the facility, airport security officials said.
The officer who was wounded and later died was identified as Fidel Rojas, while the two other officers were identified only by their last names - Matadano and Villa.
The Public Safety Secretariat confirmed in a statement that three officers were killed at the airport, but it did not provide details on the assailants.
Shots were fired when Federal Police officers "who were conducting investigative work went to detain individuals probably linked to the crime of drug trafficking," the secretariat said.
"Upon seeing themselves surrounded by the Federal Police, shots were fired at the federal officers," the secretariat said.
The Public Safety Secretariat, however, did not say whether the shooters were also law enforcement officers.
Mexico City's Benito Juarez International Airport is the country's largest airport, handling more than 25 million passengers annually. EFE