Later sources claim that after an initial defeat , Gallus and Volusianus were murdered by their own troops ; or Gallus did not have the chance to face Aemilianus at all .
Gallus ' ' army went over to the usurper .
Later sources claim that after an initial defeat , Gallus and Volusianus were murdered by their own troops ; or Gallus did not have the chance to face Aemilianus at all because his army went over to the usurper .