I disagree.
Teal shirt dude was clearly the aggressor. Moving towards someone in a threatening manner is legally Assault. Physical contact is battery.
If I recall from the video, the husband had the gun pointed down and the ex got in his face and then tried to take the weapon from him.
Offensive contact, a threat to take the gun and use it. He had the legal high ground, up ‘til then. I’ll be curious to see if he has a history of violence.