Meanwhile, a fourth CH-21 returned to Ap Bac to attempt to rescue the downed helicopter crews, and it too was heavily damaged by ground fire and forced to land on the muddy rice field. The VC had set a new record: the battle was the first time they had either destroyed or downed five helicopters within a few hours. At 13:30, Ba's M113 formation finally closed in on the downed helicopters on the west side of Ap Bac. The M113s approached the landing zone in single file instead of in formation, and they were immediately fired upon by VC inside the hamlet who were able to concentrate their fire on one target at a time. The South Vietnamese M113 gun crews were exposed from the waist up, so they were easy targets for snipers; by the end of the day, 14 South Vietnamese M113 crewmen had been killed due to their exposure. The two leading M113s were able to pull up beside the downed helicopters, but one driver was killed while driving with his head outside of the hatch, and Ba was knocked unconscious inside his carrier.