While Reno's attack started down the valley, Custer and his battalion (Command element, C, E, F, I, and L troops) moved to their right (to the North, heading west in Medicine Tail Coulee) to gain a position to attack the (they hoped) rear of the village.
As Medicine Tail Coulee opened up as it opened to the LBH river, Custer broke up E troop into its two constituent platoons. The first platoon, E troop (under Smith) was originally diverted a bit to the North in the coulee to drive off a small group of warriors. 2nd platoon, E troop (under a very new Lt. Sturgis) was directed toward the Medicine Tail Ford. Sturgis stopped a couple of times as his command (only around 20 men) neared the ford. It seems obvious to me that Sturgis was a little taken aback by what he was hearing in the direction of Reno's fight, and as he neared the ford it was obvious that he was nowhere near the end of the village. But, orders being orders, he eventually started to cross at the ford. It seems around 15 to 20 warriors had gathered on the village side of the ford, and started firing as 2nd platoon started to cross. One of the first to get hit was Sturgis, and warrior accounts seemed to focus on another leader also getting hit (the platoon sgt?). At this point, the remaining troopers gathered the wounded/dead and fell back. This is surely evidence that Custer was still dictating the flow of the battle, and retained command initiative. E troop's "assault" was clearly an attempt to determine the extent of the village. If successful, I have no doubt that Custer would have pitched in with the rest of his command. From his remaining troop's position in the Coulee, Custer would have been observing the failure of Sturgis' attack. I think this lead to his decision to continue up the ridge and find the extent of the village and find the next best place to attack.
A view towards the LBH river, and Medicine Tail Ford. E troop, 2nd platoon, would have approached the ford directly away from the viewer's perspective. Custer would have been located a bit further back (behind this marker), observing the flow of battle.
A zoomed in shot towards Medicine Tail Ford. E troop, 2nd platoon approached the river through here, attempted to cross, and fell into disorder and confusion when its command element was eliminated. After some inconclusive skirmishing from 2nd platoon and 1st platoon (which moved toward the ford for support), action here faded away as the reconstitued E troop moved back toward the rest of the battalion.
Next post: We continue with the battalion as it makes its way up and along the ridge.
I should point out that the battle "narrative" is my interpretation, based on reading, but more importantly what my eyes told me looking at the ground. I make no claims for consistency with any single source, nor do I claim ultimate accuracy. Most of this just seems like common sense.....to me!