Why are you surprised? He is growing up....he has an extremely strong pedigree full of dogs known for aggression and strength....he is not a Lab or a Golden
If you are planning on neutering him, do so.....
Personally, I would not tolerate this behavior.....I believe in positive training, but also in consequences. This is behavior you do not want to tolerate....yes, a prong correction could ramp him up. But I am a firm believer that redirection and reward can backfire as we really do not know if the distinction between unwanted behavior and desired behavior is crystal clear to the dog. Even a verbal reprimand helps - but not a quick glance away and reward....I have seen it backfire on people.
Do not put him in a position to fail....only to win. Do some private set ups and corrections without being in a big AKC class - get control over him before letting this happen again.
Probably not the most popular answer here.....
Csabre Sch1, Hexe Sch2, SG Bengal, Lynx, Komet, Kira HGH & Kougar v Wolfstraum ~ Ziberia IPO1 ~ ATB Basha, Kougar & Kyra, Fenja, Sch3s, Cito, Sch2, Danger RH & Alice Sch1s ~Kelsey