New video from the Kansas City shooting appears to show the exact moments before shots started to ring out -- and as the cops have indicated, there are teenagers in the mix here.

TMZ has obtained footage that depicts the KC rally Wednesday at 1:48 PM CT -- right around the time the first reports of a shooting came in -- and eyewitnesses tell us that the young guys you see in the background got into a heated exchange with someone off camera.

There are a few key players to focus on -- a teen in red, who you can see get angry and throw his bag down as he argues with someone who's not in clear view. There's also another teen in all black with a satchel-like bag hanging from his side, who walks toward the action.