First, make sure it's safe, with no further avalanche danger to yourself or others, before you entering the area. You don't want yourself or anyone else to also fall victim. You want everyone in your group to stay there to help with the rescue. Don't send anyone out for help at this point. Every single person is needed for the search and digging.
Time is of the essence.
By the time someone got out to contact an outside rescue party and that rescue party readied itself and arrived on scene, they're going to be helping dig out a dead body. Search in an organized manner. Go to the place the person was last seen. Turn your beacons to receive. Mark this spot where the person was last seen for future reference.