Okay, this is my interpretation of the
little ones attack at the windmill and how it played out.
Glen is immediately attacked and killed. Jay and
Datu open fire possibly striking but not killing the little one. Next Jay is attacked but not killed. Datu gets a couple more shots off but is soon firing blanks. Datu is struck down by the little one, causing the scratches to the neck and face dropping his pistol as it skitters along the ground. The little one approaches Datu and picks him up but is attacked and killed by Jay and Datu is dropped back to the ground. Jay approaches Datu and we hear him scream as he’s bitten by Jay. Jay then runs off from Datu but not leaving the scene entirely. The beeping sound is from the windmill as some component on it is failing and giving off a beep, maybe the pump burning out. Next episode, Datu yells for Jay to kill him. But I think what made Jay not kill Datu, only biting to turn him, is what keeps him away despite Datu’s pleading. Datu then turns the Mata-gun on Jay, killing him.
I don't think the Mata-gun was used to kill the little one. It's pretty clear to me that I don't hear it fire, until Datu kills Jay. I think that Jay used a tool, which made a wound that looked similiar to that made by the Mata-gun.
(Jay may not have been fully turned thereby still having enough conscience remaining to attack the Little one and move away from Datu after only one bite. Maybe thats why Datu is turning as slowly as he is....or he was fully turned, he sounds like it, but still had some control, or there was some other function at play to just turn and not eat)