I believe sKerry scooted downstream at flank speed for about 5 km.
A few hundred yards would be one thing - .50 cals shoot a long way. But 5 km is something else entirely. I'm not sure how fast PCFs were, but that sounds like he ran for 4-6 minutes - an eternity in an ambush.
I formulated this just looking at the diagram. The WP did Kerry a favor by not saying how far and how long he ran. If they said he ran for 5 klicks before rushing back to support the other Swifts, it looks real bad.