He does sound credible and that bit about the blood in the bathroom is intriguing.
To me it sounded like those cops were looking at him as a possible patsy. As in, they need someone to hang the “second shooter” accusation on because they know, or fear, that soon it will be impossible to hide that there was.
My speculation only.
I agree. If you read the comments section on his YouTube video in the link everyone is telling him to not talk to any law enforcement from now on without a lawyer present for the very reason you suggest, setting him up to be connected to a second shooter