The video above shows how it looked inside Ohio River Fireworks just hours before tragedy struck.
A day later, on July 3, 1996, 24-year-old Todd Hall carried a lit cigarette into the packed store in Scottown, Ohio and ignited a stack of fireworks.
Within moments, the store that was stocked from floor to ceiling with fireworks was engulfed in flames. The prank ended up killing nine people and injuring many more.
Hall, who suffered a brain injury in a skateboarding accident, remains confined to a mental institution after being ruled incompetent to stand trial.
The tragedy grabbed national attention, highlighting the need for stronger laws dealing with the sale of fireworks.
Laws that have since been strengthened to hopefully prevent this from every happening again.