Sam - They didn't actually mean to kill Nathan, they just thought he was trying to stab them and panicked

Henry - He always just hated Austin

Will - He desperately wanted to play soccer again and was willing to kill someone for it

Hana - She wanted to test out her new poison, and Jane was annoying her

Jae - He only meant to kill Isamu, but had to kill Yoshiko too because he was a witness

Cooper - He thought he was smart enough to get away with it