Boston - The massive manhunt for the perpetrators of last year's Boston Marathon bomb attack exposed some "fault lines" in co-ordinating law enforcement at the federal, state and local levels, according to a study released on Thursday.
Emergency responders racing to a crime scene without waiting for orders might save lives by tending to the wounded, but also risked being shot by police, the Harvard University report found.
The dangerous events after the bombing began three days later when the two accused brothers shot and killed a university police officer in a failed attempt to steal his gun and flee the city.
The shooting prompted hundreds of local police, as well as law enforcement officials who had travelled from other towns to assist, to race to Watertown, Massachusetts, where the suspects traded shots with police.
Officers surrounded the suspects, placing police at a high risk of shooting one another, the report found.
"They were incredibly lucky that there weren't a lot of friendly fire casualties," said lead author Herman "Dutch" Leonard.
The study was based on interviews with some 100 law enforcement and other public officials who took part in the response.
One officer, Richard Donohue, was badly wounded in the gun battle and witnesses told local media that he may have been accidentally shot by a fellow officer.
The gun battle ended in the death of one suspect, 26-year-old Tamerlan Tsarnaev, while his younger brother Dzhokhar, now 20, managed to elude police.
When the younger brother was found hiding in a dry docked boat the next evening, dozens of police raced to the scene.
One officer on a rooftop fired at Tsarnaev, prompting "a substantial volume of contagious fire" by other police at the scene, the report found.
It noted that contagious gunfire, in which the sound of shots prompts others to fire their weapons, poses a high risk in densely populated areas such as the Watertown suburb of Boston where the younger Tsarnaev was apprehended.
That incident was not the only case in which possibly overtired officers ran the risk of shooting one another, the report said.
Years of planning
Despite problems during the manhunt, the report found that law enforcement officials worked together smoothly on the day of the bomb blasts, evidenced by the fact that most of the casualties, many of whom lost legs, survived despite substantial loss of blood.
That coordinated effort was a result of years of planning and coordination around the marathon, Boston's best-attended sporting event.
The Harvard report suggests that law enforcement officials responding to major security threats take more aggressive steps to establish tactical command, including planning rest shifts so that they are not relying on overtired officers.
The lessons of the response to the Boston bombing could easily apply to future security scares, Leonard said.
"Any significant terrorist activity on the homeland is going to generate a similar ramping up and presence of many different law enforcement agencies," Leonard said.
"This event illustrates how much progress we've made since 9/11 and Katrina in being able to form rapid command structures that are effective," he said. "But we have a lot of work to do in projecting the same philosophy down to operating on the street."