Peter was trying to get out of his bad habits and not do anything bad to your friends or loved ones due to jealousy and his sick obsession.
But he was getting tired of seeing you together with everyone else and not with him and loving him..and he just wanted to kidnap you to keep you to himself.
As he sat in the cafe waiting for you as usual to share a shake with you. He saw you and Tk talking and flirting together and that was Peter’s breaking point..and he planned to get rid of Tk..
After a week passed and while everyone was at the Christmas party you was having Peter was in charge of the drinks and grabbed a bottle of poison and poured it all into Tk’s drink. And grinned at you sweetly knowing you didn’t know his plan as he walked towards Tk.
“Here you go, hope everyone enjoys~.” He said to you all and turned away leaving back to the kitchen after giving everyone else their drink. As he grinned wickedly to himself.