I suggested the possibility of an air gun to my son at the time. However, I thought the shots had come from within the rally compound. I forget how effective for snipers an air gun would be at, say, 200+ yards... could help explain the head shot.
Some media dweeb immediately identified the weapon as an AR-15🤷
On second, third and tenth listening, it has become clear to me that the audible shots were heard before President Trump grabbed his ear.
For this reason, and because of other videos that have appeared along with audios, I no longer suspect and air gun.