When the battle started, Carter had this mentality to stick to the plan. When he heard Owen's shouts, he immediately followed the source of the voice. Still, he remained vigilant in case he would meet Ryan on the way.
BANG! BANG! BANG!
Three consecutive shots were fired, nearly deafening him as it sounded just like real guns and bullets. Luckily, Carter's instincts were all heightened. Therefore, he heard the faint noise of a grunt as Owen managed to shoot Ryan, albeit, he guessed it was a mere graze.
He then heard Owen's body slumping to the floor, as if hiding somewhere. Since Carter detected the presence of the two by the sound wave of two figures, he didn't hesitate to come out from where he was hiding.
BANG!
