The Port Authority of New York and New Jersey on Tuesday marked the 20th anniversary of the first terrorist attack on the World Trade Center.
On February 26, 1993, a bomb exploded inside an underground parking garage at the complex, killing six people and injuring more than a thousand others.
The explosion forced tens of thousands to be evacuated from the buildings, a grim foreshadowing of what was to come eight and a half years later.
Several of the plotters were caught when investigators connected them to the rental van used in the attack.
Six were later convicted.
Police Commissioner Ray Kelly was also the city's top cop back then and rushed to the scene that day.
He says terrorism wasn't immediately assumed. But even after the attack, Kelly says it didn't turn out to be the wake-up call it could have been.
"In a sense, we pay the price. Not that the public needed to be totally engaged in it. But governments - federal, state and local - were not doing enough to look over the horizon," Kelly said.
The Port Authority held a morning mass at St. Peter's Church, followed by a moment of silence and the presentation of a plaque to relatives of the six people killed during the bombing.
The victims included a pregnant woman who died with her unborn child.
"It's hard to forgive, it's impossible to forget. I'll always remember my dad that day, that's why I'm so glad that we do this every year. Forgiveness is a little more difficult," said Michael Macko, whose father died in the bombing.
"It's still like day one because you know what I realize what his family has missed not having him around," said Nancy Burroughs, whose brother was killed in the attack.
The World Trade Center's 9/11 Memorial and Museum will feature a section devoted to the 1993 bombing when it opens next year.