Agent Fitts says that ERT recovered a shell casing from a Bushmaster AR-15 from the scene where the border patrol agent was shot. But Anthony Noel was not using an AR when he shot the border agent, he was using a handgun.
A Federal Firearms Licensee (FFL; the gun store owner) may not ship a handgun to an address. The weapon must be shipped to another FFL, and the purchaser must pick it up and sign for it at the second shop. There is no way the gun store owner would mail a handgun to "Occupant," and that it would be left on the porch.
Episode is full of anti-gun propaganda. A gun ordered on the internet cannot be mailed to a person's home address by an FFL dealer, it must be signed for at the store after a background check is done. Agent Fitt also says that records show the gun dealer shipped armor piercing ammo to the suspect, which is absolutely impossible because armor piercing ammo is illegal in every state. If the dealer sent armor piercing ammo he would have been doing so illegally therefore there would not be an official record of it.