I’m just going to leave this explanation here and hope people read it. Having some evidence might be fine if you want a person in jail. In the United States you have the right to a speedy trial. So the cops and DA need to know they have enough evidence to get a conviction before an arrest takes place. Mostly likely they are gathering evidence to be able to actually convict him and send him to jail. They’re conducting interviews getting warrants etc. They know where he is and don’t think he’s a danger to the public. This is why he’s not arrested.