Upstanding, privileged, inner circle Korean Workers Party members in Pyongyang (a city where only loyal communists can live), judging by the good quality of clothes, the health of the little girls (Young Communist Pioneers). It may be sincere if they personally knew the Chia Pet, or it could be faked and staged. It could be a comination of some level of grief, but then hyped to the next level through acting, based on seeing whatis going around oneself (mass psychosis) and also knowing what the penalty would be for not showing saddness and dispondency.
That pretty much explains it.