sir at that time i was standing inside my launch.....
and one more reason for their BOOM could be their low altitude flight
,because when i saw them they were flying at quite low....altitude
but i am still sure that their speed was surely above 1 mach(above sound barrier)
i actually today did listen a real sonic boom...........like sound by an aircraft when i went outside and looked up there were two mirage-III gray color scheme fighter aircraft...it was just an awesome view to see them flying in such high speed