[SWHouston]

Ummm ok, I'm getting a little better picture of this now...

It appears that you just can't let him charge the intruder, that right ?
He's attempting to go out into an unprotected/unconfined area, right ?

IF I'm reading this right, then you should create a signal/instruction to "back him off". I use a physical touch on their noses (not verbal), to suppress their vocalizations, when it's appropriate. IF it's actually a real stranger, or something that is in territorial violation, I just don't suppress them, they usually quieten down after I arrive.

When in the training process for their ability to distinguish the level of threat, when they don't respond to the suppress command, they were led into an area, where a door could be closed between them and the cause, and left there for a while. They REALLY don't like that ! You can release them after the cause has gone.

The key is practice here, I think when they know you're going to respond to the alarm, you'll be better able to get this under control. It's going to take time for them to "trust" you, and realize that the "Leader" has arrived and they can stand down and look to you for instructions.