I doubt that it is the case here but with substantial practice an experienced shooter with a semi auto is almost indistinguishable from full auto
Buddy timed me firing 14 rounds in less than 3/4 of a second regularly as well as 6 out of a 357 revolver in 5/8 second. It sounds different first few times you hear it.
Those were clearly full auto. Rate of fire too high for anyone, experienced included.
Drop-in FA for Glock exists, and the RoF is extremely high. Way easier for thugs to buy that than practice their way up to low FA rate.