His Penis got extremly hard and tented his boxers, but he didnt start to masturbate right away. Instead he lifted his boxers and ripped them apart. He saw no point in not ripping them apart, because he would some time in the future be a horny male german Shepherd.
He was shook by his newfound strenght and started rubbing his member. It was hard as if a bone was in it and dusted with beige fur. His cock grew from its original 5 inches to humoungus 8 inches witha big and long sheath.
His sheath slowly attached itself to his lower belly while he stopped masturbating. He got up onto the ground on all fours and started humping the air.
His cock was fully dog now and his moans sounded more and more like howls and barks.
Furthermore his still human balls started to grow and grew beige fur just like his penis and taint.
Then a short loud howl erupted out of his changing mouth as his last human seed shot out of his cock.
He howled out of pure exstacy and didnt stop humping the air as his canine balls were filled with canine seed.
His orgy stopped aprubtly as a howl was heard coming from just around the street.