A power vacuum was created in the Western Empire after the events of 454 and 455, which saw the consecutive murders of Aetius and of the Western Emperor Valentinian III, who had been responsible for the "magister militum's" assassination. After the assassinations, the Roman Senator Petronius Maximus proclaimed himself emperor. Petronius, however, was killed by a Roman mob immediately prior to the Vandal sacking of the city in 455. After the sack, the Visigothic King Theodoric II proclaimed as Emperor Avitus, the Roman military commander in Gaul. In return for Theodoric's support, Avitus agreed to allow the Visigoths to enter Suevi-controlled Hispania. Theodoric consented to Avitus's offers and the new emperor, with the Visigoths under his command, marched on Rome to secure the throne. Avitus named the Visigoth Remistus as "magister militum", a position which had been vacant since Aetius's death.