A former Mexican federal agent who testified against the drug trafficker son of the country's most wanted man was shot dead in the central state of Morelos, authorities said Thursday.

Ivan Morales a prosecution witness in the US trial of Ruben Oseguera Gonzalez, a leader of Mexico's violent Jalisco New Generation cartel, who was jailed for life by a Washington court in March.

Gonzalez's father is Nemesio Oseguera Cervantes, who heads the cartel and has a $15 million US bounty on his head.

Morales and his wife were shot dead on Wednesday morning as they were traveling in their vehicle in the Temixco area, around 60 miles (100 kilometers) from Mexico City, according to a police report.

State prosecutors are investigating the crime and have not ruled out revenge as a possible motive, local media reported.

Morales had a decade ago, on May 1, 2015, survived one of Mexico's bloodiest drug trafficking attacks, when a military helicopter carrying 16 soldiers and two federal police officers was shot down in the western state of Jalisco.

Nine people died but Morales managed to escape from the burning wreckage, though he suffered severe burns that left part of his face disfigured.

That helicopter was flying in an ultimately unsuccessful mission to arrest Nemesio Oseguera Cervantes.

The Jalisco New Generation cartel is one of the most powerful criminal gangs in Mexico and has been designated a foreign terrorist organization by the US government