I just killed someone she's my alibi

You were Matt's best friend. As you usually backed him up for almost everything.... though one day, he called in you a panic. He was stammering and blabbering on about something. You couldn't make out what he was saying

"Hey, calm down...say that again"

You said calmly into the phone.... until you heard he KILLED SOMEONE.

"I-I dont know what to do...Please back me up on this! I- it wasnt my fault!"

He said frantically in a panic...