How does the newcomer pry the bulldog’s jaws apart?

From the text:

Tim Keenan continued standing over him, but Scott took no further notice of his presence. He had managed to get the muzzle in between the jaws on one side, and was trying to get it out between the jaws on the other side. This accomplished, he pried gently and carefully, loosening the jaws a bit at a time, while Matt, a bit at a time, extricated White Fang’s mangled neck.