I don't think there was a command. I think it was a reaction. My son's little dog is a Mini Australian Shepherd. Even if I am playfight with my son, she will come at me like no one's business. (Luckily she is pretty tiny!)
That said, I feel that a scuffle ensued shortly after John arrived at 34F. I think he went into the basement, or perhaps even around the backyard if he was summoned by someone over by the gate to the right side of the house by the garage. I truly think he was in that basement. But when the scuffle ensued, perhaps some tried to break something up and there may have been 2 or more people in the mix. I think Chloe got excited, jumped up to defend her master and tried latching onto JOKs arm, as they are trained to do. Due to the commotion, however, she never was really able to latch on and her teeth may have just grazed his arm and her claws scraped him up at the same time. Picture the dog lashing at the victim, with arm raised to protect the body, mouth in center trying to bit, paw on either side taking a swipe.
I think that is when JOK fell and whacked his head on something, likely a piece of exercise equipment. He bled out, they all panicked and I think the initial aggressor got out of dodge while the grownups "handled" the situation. I think they acted naturally until everyone went to bed. The calls between the 2 Brian's I am thinking were pretty quick. "Is it taken care of?" "Yeah, all taken care of."
The initial perp returned to the scene to help make sure everything was handled, meaning, he pulled up to the curb, and JOK was dead or close to dead. They dragged him out the bulkhead in the back yard, through the left side gate and straight out to the flagpole, as far as possible from the home.
Too bad they forgot about the snow plow guy.