Once, a long time ago, Peter had felt another moment such as this--when he had buried his fangs in Jed Hawkins' leg to save Nada.
In that fraction of a second which carried Peter through space, Corporal Cassidy's finger was pressing the trigger of his automatic, for McKay's gun was half out of its holster.

He was aiming at the other's shoulder, somewhere not to kill.
The shock of Peter's assault came simultaneously with the explosion of his gun, and McKay heard the hissing spit of the bullet past his ear.
His arm darted out.

And as Peter buried his teeth deeper into Cassidy's leg, he heard a second shot, and knew that it came from his master.
There was no third.

Cassidy drooped, and something like a little laugh came from him--only it was not a laugh.

His body sagged, and then crumpled down, so that the weight of him fell upon Peter.
For many seconds after that Jolly Roger stood with his gun in his hand, not a muscle of his body moving, and with something like stupor in his staring eyes.