I just heard something terrifying. A missile, or a rocket, or a fighter jet....but

LOW overhead...and louder than anything I have ever heard in our skies before. It got increasingly loud as it broke the sound barrier...but not stopping for quite a long time. It sounded as though it was moving north to south...makes no sense...but incredibly frighteningly loud.

I should add that the sound went on and on and on. It kept getting louder...in the most terrifying way. It rumbled and almost seemed to shake the air around my building.