The conclusions, obtained by The Associated Press, are from an internal Coast Guard review that looked into the events and actions that led to false news reports of gunfire in Washington on the anniversary of the Sept. 11, 2001, terror attacks.
The Coast Guard unit that conducted the training exercise was not aware President Barack Obama would be traveling to and from a memorial service nearby. The agency concludes that if the unit had known where the president would be that day, it would have rescheduled the exercise.
The incident spooked the capital, sent FBI agents to the scene and grounded some flights from Reagan National Airport.
Erroneous live cable news reports on CNN and Fox on Sept. 11 had said that the Coast Guard was firing shots on the river. CNN reported the Coast Guard had fired 10 rounds at a suspicious boat, and showed vessels circling in the water - near the bridge Mr. Obama's motorcade crossed on the way to a memorial at the Pentagon earlier that morning.
The president was not in the area when the training exercise took place, the Coast Guard said.
A group for military families expressed outrage that the training exercise was held near the Pentagon at the same time families of those who died during the Sept. 11 attacks had gathered there for a memorial.
"September 11th is a day to remember the loss of 2,973 innocent victims in New York, Pennsylvania and the Pentagon; not a day to create an unnecessary panic near a terrorist's target," Military Families United said in a statement.
The confusion was reminiscent of an event earlier this year in New York, when a presidential plane was flown low over the city for a photo shoot and some people feared the city was under attack.
In late April, a huge presidential passenger jet and two F-16 fighter planes whizzed past the Statue of Liberty and the lower Manhattan financial district as part of a photo shoot, sending panicked office workers streaming into the streets and evoking memories of 9/11.
After that incident, Mr. Obama saidand promised it would not happen again. The director of the White House's military office resigned after the incident.