Six uniformed police officers heard the message and immediately began knocking on doors and evacuating residents.
Ms Williams, still in her pajamas, and her family grabbed their cat and made their way to their car to leave the immediate area.
She said she saw police cordon off 2nd Avenue to prevent anyone from going down it.
David Malloy was out walking his dog, a black German shepherd named DJ, when he noticed police cars on every corner.
Then he heard a voice that he thought was coming from a police car telling people to evacuate and please stand back.
Smoke rises from downtown after a reported explosion in Nashville.(Andrew Nelles/The Tennessean via AP)