Brian could tell that one was different.  After all, he wasn't in human form.  The guy looked like some weird hybrid of the two.  Rather than say anything to give himself away, Brian simply took off like a rocket!  The growl didn't come until the end when Brian tackled the much larger guy to the ground.  Not that he'd be able to accomplish anything, but Brian began to pummel him as best he could.  Fists were driven into ribs, kidneys, anything and everything he could do.  Little did Brian know that one little swipe from that creature's claws and his entire life would change as well.