Police are now hoping surveillance video could help find, who did it.
A private security camera captured it all. A cyclist approached the marine recruiting office at around 3:40 in the morning. He stepped off the bike, walks to the building, then leaves. Moments later there was an explosion.
New York City Police Commissioner Ray Kelly said, "This was not a particularly sophisticated device. It was a low order explosive in an ammunition box similar to this." The front window was destroyed, but no one was injured.
Then late Thursday night, authorities made a discovery: several member of congress received what appeared to be greeting cards, with a Hollywood return address. Inside was a political manifesto against the Iraq war and a photograph of a man standing in front of that same recruiting office with the message "Happy new year. We did it."
Friday morning, authorities said they found no link between the mailings and the bombing. The incident is remarkably similar to two recent bombings at the Mexican and British consulates in New York City.
In all three cases, a lone man on a bicycle attacked in the early morning hours, using low intensity explosives. "We don't know what's motivating him to do it and we don't know what's in his mind. At any moment, at any time, he could escalate to the next step and unfortunately, we don't know what will trigger that," said former FBI Agent Brad Garrett.
Investigators are also looking north to Canada. ABC News has learned that a recent border stop yielded evidence linked to the incident, and that authorities are now looking for individuals in connection with the case.