Henry was the killer-Wakefield's son. My theory was right that means, although the kills weren't a result of blacking out, like he said he did when JD died, but he did it on purpose.

He told Trish, before he kills her, that he killed her father and JD because they could ruin the wedding, or something along those lines. This later proves to be seemingly false, since he was just using Trish as a pawn in his game to get Abbey to the island.

He loved Abbey-how he loved her wasn't explained. If he wanted to marry her or something, or if it was simply a sibling love, wasn't explained. I'm leaning towards the former, however disturbing that was.

As he looks to be about to kill Abbey after he killed Wakefield and faked the deaths of he, Abbey and Jimmy (Jimmy was to sign a confession as Wakefield's accomplice, since Shea and Madison survived and would claim there was an accomplice to let him out of jail).

Jimmy attacked him, and they fell off a cliff or bluff or something. Abbey ran down, and rammed Wakefield's knife-which Henry threw down a little earlier-into Henry. He dies as he says he loves her.

Jimmy and Abbey are on the coastguard boat together, leaving the island together.

It cuts to the camera from the yacht, showing the main cast talking about the wedding, giving their regards and stuff. It ends with Henry talking to it, about the wedding, on the island already. He smiled to Trish-as he was giving the message to her-and it freezes, zooming in on his face.

Cut to credits.

 

So, the list of survivors:

Abbey

Jimmy

Shea

Madison

 

Deaths of the episodes:

Danny: Wakefield fights him as he breaks out of the prison (Henry slipped him the key). They fight, Danny smashes a phone into his face to knock him back and buy Madison and Shea time to escape (since the women can't shoot for some reason). He grabs Danny's head, and slams it into a spike on the desk to kill him.

Trish: Henry runs out to search for Wakefield after someone crashes into their housing's door. He grabs the gun, runs out, and tells her to lock it. She does, and soon, Wakefield kicks it down and runs after her. She slips out the bedroom window of the little house they're in and runs into Henry (minus his gun). He has his knife (a small one, not the boarding knife Wakefield uses) and stabs her in the side after confessing to her.

Sully: He and Henry go to where the coast guard helicopter will land, and Henry confesses to him. Sully thinks it a joke, until he sees the knife. He shoots, but Henry removed the bullets at the shack. He says Wakefield's behind Sully. He says he's not stupid, but Wakefield tells him he really is there. He was about to swing the gun at Henry, then turns around, then he's stabbed by Henry.

Wakefield: Henry betrays him after he shoots at Jimmy in the burning church (Jimmy rammed a flare at Wakefield, burning him (you could see the burn on his chest) and then throws it. He runs and is shot at by Henry, left for about ten minutes, then it reveals him alive, imprisoned by Henry. As they catch up to Abbey, Wakefield behind her, her stabs at her, and goes past her, stabbing Wakefield to kill him.

Henry: As he walks to Jimmy and Abbey on the rocky beach, she grabs the boarding knife and runs him through.