When handing them the box with the syringes, Sin had told them nothing about how to use them, whether one had to inject all of the liquid into one person or if it was supposed to be used multiple times. None of the gang members present had ever heard about a syringe with a liquid being used to turn someone into an Altered.
As such, the first thing Raven wanted to do was test out how effective just a little bit of that unknown substance was by using a stranger. After the earlier exchange he had a good estimate on Austin’s power, so he considered him to be the perfect test subject. This way, he could gauge for himself how much more powerful the other had gotten after the injection.
He had pulled out the syringe that was in his hand and slowly crept his way up to Austin. It was pretty crowded but not so packed that moving was impossible. Fortunately, everyone's attention was still on the first fight.