 In 237 or 238, Gordian went to the province of Africa Proconsularis as a legatus under his father, who served as proconsular governor.Early in 235, Emperor Alexander Severus and his mother Julia Avita Mamaea were assassinated by mutinous troops at Moguntiacum (now Mainz) in Germania Inferior.The leader of the rebellion, Maximinus Thrax, became Emperor, despite his low-born background and the disapproval of the Roman Senate.