Complex sentence: The incipient decommissioning process was torn down on December 16,2016, at Louhossoa/Luhuso, when five civil activists were preparing the deactivation of an important quantity of weapons (about the 15% of the arsenal) they were arrested.
Split into simpler sentences: The incipient decommissioning process was torn down on December 16,2016. At/Louhossoa, when the civil activists were preparing the deactivation of an important quantity of weapons (about the 15% of the arsenal) they were arrested.