given the rainbow trajectory & generally quite short range of muzzleloading rifles (i have 3 of them) i find this report "questionable" at best & "highly unlikely" under any circumstance.
while i fully understand that "falling bullets" CAN & DO kill, i've seen no evidence that a typical ML bullet would travel a mile under any "upward angle of fire" whatever.
fwiw, when i was stationed in LA during the Olympic Games in 1983-84, we had two people in the metropolitan area KILLED & several people injured by "falling bullets" fired from centerfire rifles, which were shot "up into the air" to "celebrate the holidays". - this foolish/common practice seems to be an "LA thing".
(one of the "injured" was a civilian security guard, who worked for our military headquarters command, who was "making his rounds" about 2300 on NYE & was struck by a .30 caliber bullet in the left shoulder, near the collarbone. - thankfully, he was NOT badly injured, was treated at a local ER & returned to work 2 days later.)
i don't think that i have to say this to our forum members, BUT to any "lurkers", "shooting up into the air" for ANY reason is a REALLY STUPID & dangerous thing to do.
It is also apparently a pretty common phenomenon in other parts of the world, for celebrations among other things...
Death Blossom : The tendency of Iraqi security forces, in response to receiving a little fire from the enemy, to either run away or do the "death blossom" spraying fire indisciminately in all directions. The term originated in the 1984 movie "The Last Starfighter" as a maneuver in which a single starfighter can single handedly wipe out an entire armada.
I don't recall hearing F/A around where I live, but I have often picked out that particular rhythm of a string of gunshots among the fireworks. Given that I live under one of the approach paths to the airport, I hope nobody's flying right at midnight on New Years.