Cruel Summer Killer

 Let's look at the facts as they stand...

1) The killer was present Tuesday and killed a girl in Forest Green with a bow & arrow.

2) They snuck up behind Popko, killed him, anchored his body to the raft but attached something that brought him to surface on Friday.

3) Tori was tricked into a pit trap.  The pit had to be dug before Chad and Sienna arrived as they were the first to show up.

4) Ann was with Jackson prior to the storm but somehow got to the second floor of the main hall before Miranda, Ethan, and Rocki showed up.

5) Jackson disappears shortly after he is seen with Ann by Ethan and Rocki.

6) The Generator room was obviously rigged to blow up before the power to the camp was cut.  But how many people were supposed to die?

7) Popko's body was set up as the killer surmised more than one person would go start the generator or make a break for it in the cars.  The plan was to divide and kill.

8) The killer is unaware of the satellite phone.

9) In the case of the survivors opting to make a break for it in one of the cars, both cars had two tires popped on the sidewalls so that only one car could be made functional.  They also had their gas tanks drained.  The gas was then used to set the Range Cabin ablaze.  This became paramount when they learned about the satellite phone.

10) After the three survivors left the cabin we see the killer's perspective in the ruins of the Range Cabin.

11) The killer was then waiting by the girl campers cabin to set the gas trail ablaze.  They hoped to once more take out the remaining counselors.  Because Chad leaves Sienna and Rocki they are forced to ignite the fuel with only one person in the car.

12) Annoyed that Sienna was not in the car, the killer made the assistant manager suffer before finally putting the kill shot through her heart.

13) The chapter ends with a knife to Rocki's throat... 

So, any guesses on who the killer is or possible motives?