It's unclear why the altercation happened, but something had to have been brewing between the teammates.
Based on the footage from the game, this was no sucker-punch incident; these dudes were squared up ready to box each other while their other three teammates ran a motion offense.
The whole thing was over in a matter of seconds, and it doesn't appear any solid blows were actually landed. Henry fell down during the melee, but that might have been more from a shove in the back as people came in to break things up.
If Game is looking for a new album title, though, might we suggest...The Sockumentary?