Someone spawned in key room during raid in front of me

I was at reserve, 15 minutes before raid end. I was in the RB-AK key room. I closed the door when ı enter the room. I heard someone running below me so ı stopped and listened to the walking noise and suddenly someone appeared in front of me . I killed the guy. And he had an ash and lvl 4 armored rig full of magazines and medicines. I checked the door and it was closed. After the raid ı didnt see his name on the kill list which is super strange ı have no idea what happened. Maybe some of you guys know what it is. (Room was locked before ı enter and ı looted the whole room so its İmpossible for someone to be at there before ı enter.)