Morgan Wallen Chair Throwing Witness Speaks Out, Cites No Real Reason

Morgan Wallen didn't appear to have any real reason to throw a chair off the rooftop of a Nashville bar -- so claims a security guard for the joint ... who's relaying what witnesses said.

Michael Phillips -- who works security for the newly-opened Chief's Bar in Downtown Nashville -- came on "TMZ Live" Monday to give us the rundown of what he says he saw Sunday night ... when MW was arrested for allegedly chucking the chair down into the street.

He says he didn't even realize it was Morgan at first, but tells us the guy went straight to the rooftop -- and that 30 minutes later ... he saw a chair land within feet of a police cruiser.

While Michael says he didn't see Morgan throw the chair in question, he does say there is security footage that confirms MW as the culprit. He goes on to cite eyewitnesses who spoke to cops -- and he gives a sense of what they told the police.

Specifically ... Phillips claims these people implicated Morgan -- and worse yet, he says they didn't see him in any sort of argument with anyone. The witnesses apparently told cops he was just being stupid ... and Phillips suspects alcohol may have been involved.

He adds ... "He was being an idiot and just threw it. There wasn't really no argument or nothing. Just him being drunk. I feel like he wasn't in the right state of mind."

Video footage and photos have surfaced that show just how high Chiefs Bar is -- with sidewalks located just below the music venue and bar -- and as you can see, it could've made for a deadly disaster Sunday night if someone had been hit.

Thankfully, the chair did not make any contact with innocent bystanders ... as it struck the ground a few feet away from Nashville PD -- who just happened to be standing outside.

For his part in the drama, Morgan was arrested on three felony counts of reckless endangerment and one misdemeanor count of disorderly conduct. His attorney says he's cooperating with investigators as they dig into this.