They apparently disassembled a remote-control toy and used the remote control along with the receiver taken from the toy to create a detonator that could be detonated from a distance via the remote. How much of a distance and whether or not the remote had to be in line of sight of the receiver has been a subject of debate, but suffice it to say that the operator of the remote was not intending to be very near the device when detonated. Others have raised issues regarding stability of such an improvised device, which would possibly explain some reported injuries of at least one presumed terrorist.
One would think that sweet little boy and all of those people who lost their legs would shake some people up!!!!