Gary had never imagined himself willingly chomping down on a person's body. They might be dead, but it still felt wrong. The fact that he could still feel residual body heat, didn’t help in any way, yet right now his life was literally on the line, as well as that of others.
If he didn’t defeat those beasts that were chasing after, then who would? Perhaps White Rose or some other Altered might be able to do something about them, but how long would it take for them to arrive and deal with the twins? How many more lives would be lost because of their rampage?
Most importantly to Gary, if he died here, then who would look after his family? The answer to that question was no one.