As far as the solider approaching the man without his weapon in hand, this is standard for the Australian Army. At least one guy has a riffle trained on the "enemy" to be searched, while an individual moves in without a weapon to search and restrain. The reason he has no weapon is:
1. have both hands free
2. not chance of providing a weapon to the "enemy".
As long as the guy moving in to do the search and restraint does not cross the line of sight of those trained on the "enemy" he is well protected.
He would obviously approach from behind and the "enemy" is made to place hands in sight etc.
Having said this every unit will have its own SOP for this type of thing, but this is the basic method that is used. If such a procedure is followed it would be very unlikely that the "enemy" could kill it would have to be "aiuchi".
Tim Atkinson
Shinto Muso Ryu 神道夢想流
Shinto Seishin Ryu 真途静心流
Gold Coast, Australia