The dynamics will change with the mix of horses. Was he aggressive with younger horses when they were added to an established herd or when it was just the two of them? Was he schooling the youngster or being downright mean? Being unfriendly and grabbing them by the neck are completely different.
If he starts out by himself, he might quickly figure out that biggest PIA yearling or goat is better than nothing. Goats need great fencing!!!