I’ve gone back through various news media reports....no one ever notes the year or model of the car they were driving. I’m in agreement....it’s extremely rare that a backfire occurs with any modern car. Also, it’s rare that when a cop turns on his siren or lights....that someone keeps driving....at a high rate of speed.
The car was a Chevy Malibu, 1978 or 79. If it has the original drivetrain the timing is adjustable, and if the car was out of tune or the carburetor hasn’t been overhauled after all these years, it could be very well be prone to backfiring.
Two Rares don’t make a right.