Let's assume a few things.
1. Non (or barely) compliant suspect.
Hold him at gunpoint until the police arrive. DO NOT attempt to restrain him. Just hold him there, as best you can, with the threat of deadly force. If he runs, he runs- be sure you can give a description. If he makes the proverbial false move, and you can articulate a perceived deadly threat, take appropriate steps to stop the threat. Tell the dispatcher you are holding one at gunpoint. Describe yourself. Describe the BG. Try to have the gun at the very least at low ready when the LEOs arrive (unless you cannot due to his actions)- preferably have it holstered or out of hand.
Do what the officer says.
2. Compliant suspect.
Hold him at gunpoint until the police arrive. DO NOT attempt to restrain him. Just hold him there, with the threat of deadly force. Order him to face away from you, go down on his knees and place his hands on his head. If he looks back at you, tell him, again, to face away from you and not look back. Change your position, if possible, and keep the gun trained on him. Tell the dispatcher you are holding one at gunpoint. Describe yourself. Describe the BG. Since the BG is looking away from you, you can more safely go to low ready, holstered, or gun out-of-hand when the cops show up. Remember though, suspects tend to not listen to instructions very well...at this point, they're having a pretty bad day, and will be doing everything possible to make it better, including try to talk to you, plead with you, look at you, get up, put down their hands, edge towards the door, etc etc etc. So don't let your guard down early.
And, most importantly,
Do what the officer says.
Of course, all of this can change based upon the situation. Common sense rules the day. Remember, the officer has no clue who is the BG and who is the GG. Every cop I know has gone to at least one run where the "victim" just happened to be the guy who called 911 first. This includes burglaries. People scoff all the time and say, "sure, who calls 911 and says someone is breaking into their place and sticks around for the cops if he's not the homeowner." An experienced cop will say "lots of people"- and he won't be lying. Think of the most Jerry Springer-worthy domestic screwed up situations...we go to those. So, until we know who is who, everyone gets out of the pool.
Oh, and remember the +1 Rule. You found one BG. Are there more? How do you know? Have you cleared the house? If you're busy holding BG #1 at gunpoint, that answer would be "no."
Mike