Probably not, I mean...those things are illegal
/s
The sound from the video definitely indicates a rate of fire from a fully automatic rifle...... whether initially designed or modified, the end result in this case would be similar.....
What’s legal got to do with what kind of weapon was used? Simply shooting a person dead from a distance is in and of itself a criminal act, absent any prior motive. To rip into a crowd only compounds the criminality, and the type of gun matters little after the first fatality, only that the score is higher if this was in fact an AK converted to “full automatic”. It is possible for a knowledgeable gunsmith, or even a determined amateur, to accomplish this task.
No law would have mattered.