Could be a typo, or it could be conflicting info. Either SOI5 and his group checked it out or they didn't. One thing seems certain, either they checked it out after the 1 guy came to them on the 11th OR they checked it out after the 3 guys came to them on the 12th.
In either case, they made the guesstimate that it was insurgents at the time, as did the uncle who was at the scene.
A reasonable assumption given the reputation of the terrorists. Given that is the odd bit of information out, I suspect that it is a typo. There were some other problems with the document - the misspelling of 'soldier'. The age of the young lady (Don't trust them on much, but I am assuming the arab media got that bit right since they have birthdates and family names.) The Arab account has it happening at 2pm. That is extremely brazen to do it in broad daylight. The 'uncle' knew how to contact the terrorists pretty quick - now didn't he. Didn't one account say they made lots of quick counter attacks and killed 40 Americans - and then another account said he had now idea it was the Americans til they started the investigation. Now which is it?