I believe the culprit grabbed a bat from the sports equipment room leaving the door open. Then went to the kitchen to grab the knives where they hid them in thier pocket. Then they went to look for someone alone for them to kill. Whenever someone asked what the bat was for, He said he was looking for a place to play baseball with a friend. Then he found our victim in the storage room. He used the bat to knock her out cold and the cleaver to make her bleed out. To make sure she didnt survive, he used the knife on her head to cause brain damage and more bleeding
There are many people who could be the killer, but im gonna go with the crowd and say Gelatin
Fun fact: the deaths werent chosen by a randomizer, I just chose the most fitting murder pairs. Like how Kenny is kinda pervy while Reddy can be mistaken for a girl