Who killed Newt?

Newt asked Thomas to kill him, and when he said he couldn't.... Newt said he would kill Thomas unless he pulled the trigger. Newt did not want to be a Crank.

“Shut up! Just shut up! I trusted you! Now do it!”
“I can’t.”
“Do it!”
“I can’t!” How could Newt ask him to do something like this? How could he possibly kill one of his
best friends?
“Kill me or I’ll kill you. Kill me! Do it!”
“Newt …”
“Do it before I become one of them!”
“I …”
“KILL ME!” And then Newt’s eyes cleared, as if he’d gained one last trembling gasp of sanity, and his
voice softened. “Please, Tommy. Please.”
With his heart falling into a black abyss, Thomas pulled the trigger.