Hello TrishPalmer and welcome to the forum. Hopefully others will chime in here that have experienced the same behavior, I have not.
From your description it sounds more like a separation anxiety reaction more then aggression. Simply, he doesn't want that person to leave. Dogs communicate with their mouth, barking, whining, biting, licking etc. I'm not excusing the behavior but it might not be aggression.
It sounds like it is the same people that he act out on. I would suggest setting up the situation and before that person gets up to leave have him come by you and pet him and talk calmly to him. Then have the person get up and leave the house without any words, eye contact with the dog or lingering by the door. If he tries to bolt to the door or them, hold his collar and firmly in a loud voice say "NO". Repeat the process each time they are leaving and when he doesn't try to run to the door, praise him verbally and with a small treat. Once he catches on that the behavior is not acceptable he'll probably stop. Most of these dogs just want to please us.