I think both the parties are allowed to shoot each other during this situation as, The NG guy was defending the trespassing and You went for a private raid.
But I saw that you were getting shot by Light Machine Gun(LMG) which may not be allowed to use at Fort Zancudo without any special event or orders by High Commands or Org Curators.
And also I would like to request the Administration who will be taking this case on consideration, to check the NG Warehouse, whether it is properly managed or getting used for personal purposes, coz I saw that he dropped LMG and 450+ LMG ammos. Who knows he might take them off duty also by saying that He got killed and was dropped. (may be was waiting for his fam members to come and kill him and take the ammunitions, and that was not Gatekeeping time also).