I’d guess at least some chance of drugs being involved.
I was just in a restaurant where some presumably meth head got a sandwich. Kept talking to the air, doing circuits around the place, couldn’t sit still for a minute, was getting himself agitated talking to the air.
I remember watching Donut Operator – an ex-cop who used to be on a SWAT team and who does commentary on a bunch of YouTube videos. He’s said a number of times that the people that he least liked having to deal with when working as an officer were the meth addicts. Really unpredictable, could wind up becoming violent after acting normal a moment earlier.