Former Philippine President Rodrigo Duterte was arrested at Manila Ninoy Aquino International Airport on Tuesday following an order from the International Criminal Court (ICC), which is investigating a crime against humanity case filed against the former leader.

Duterte, 79, was taken into custody at the airport in the Philippines following his trip to Hong Kong, The Associated Press reports.

The ICC has been investigating “massive killings that happened under the former president’s deadly crackdown against illegal drugs,” The AP said via President Ferdinand Marcos’ office. “Upon his arrival, the prosecutor general served the ICC notification for an arrest warrant to the former president for the crime of crime against humanity,” the office said. “He’s now in the custody of authorities.”