That was my impression at first too, but apparently there were around a dozen soldiers there at the time of the attack, and the three became separated. The article sort of alludes to that, but isn't really well written. If I have any of the detail wrong, someone else can chime in. I'm still unclear on much of it, and don't know whether an official version has been released.
Something went very wrong, seems either these men were left hanging without proper support, which lays the blame on commanders, or these guys got left behind in an ambush and it wasn't realized in time, also the commanders fault.