Let me guess, the shooters were law abiding citizens who had followed all the procedures to acquire a pistol permit or whatever LA requires.
La. does not require anything to buy a pistol, just an La. drivers license. La. does require a permit to carry concealed. Open carry is legal in La. and a vehicle is considered an extension of your home so you can carry a loaded weapon anywhere in your vehicle without a CCW.
To purchase and own, not a thing beyond the federal paperwork and 21 y/o requirement for handguns. To qualify for a concealed gun permit an individual must be at least 21 years of age, a resident of Louisiana for at least 6 months, pass a basic weapons training course, take safety classes, and possess no background of felony convictions, alcohol or drug abuse, and mental illness. Once approved the permit takes 10 days to issue.
I doubt they went through all that, or would have qualified if they tried. Age and felony convictions would likely disqualify them.