Or perhaps they simply didn't know. An explosive vest could have been set off by the grenade (sympathetic explosion), causing the initial report. Even a concussion grenade (if such were used) could have initiated the explosion of a vest. And during the havoc of the fighting it could have been initially thought that the vest was the killer.

Combat isn't neat and orderly, no matter how much as we'd like it to be. No combat unit -- SAS, SBS, SF, SEALs, KSK, Spetsnaz, none -- can guarantee a completely successful operation.

I'll wait a bit longer before I pass judgment, but my immediate reaction is not to overlook the possibility of a sympathetic explosion.