There's a traitor
Bob ran after stabbing the gateman four times, he went unnoticed because everyone was focusing on the man lying on the ground with blood oozing out of his stab wounds and mouth. He entered his car and drove home, when he got home he entered his bathroom, took a long bath washing the blood from his hands. He wore a fresh batch of clothes then took the dress he wore earlier to the backyard.
He threw it on the floor with the knife, he put kerosene on them and set them on fire, he watched them burn to ashes. Since the knife was not completely made of rubber, he took the remaining part, and threw it inside his trash can.
No one will know that he committed the murder, but although he thought that no one would know, his subconscious mind won't let him be, this was his first murder and he was panicking. The smallest sound makes him scared.
"What did you do?" Phoebe asked, Bob called her when he finished destroying the evidence. She came immediately.