I would definately not leave them alone unsupervised until you can figure out what is provoking Charlie to do this.
How old are the puppies? Maybe as they're getting older and bigger, they are becoming more of a threat to Charlie so he's trying harder to put them in their place. I would start treating Charlie as alpha to avoid any confusion among them (as long as the other dogs are okay with that and don't start fighting more). Give him his treats and petting first, feed him first, etc etc.
It may be beneficial to have a behaviorist out to assess the situation. I know it can be pricey, but I'm sure its worth it if it means you won't have to rehome Charlie.
Shiloh, Reece, Lolly, Skylar
and fosters Snickers, Missy, Magic, Merlin, Maya