LOWELL, Mass. (AP) - A key to preventing future attacks like the Boston Marathon bombing is to bring the crime-fighting strategies of community policing to the battle against terrorism, Boston Police Commissioner Edward Davis said Tuesday.
Davis said there are almost always some warning signs that could alert investigators of an individual planning an attack.
He said it's critical to work with communities so people who might spot those warning signs feel comfortable giving that information to police, a tactic that he said has worked in the fight against crime in Boston.
Davis said simply increasing the police presence at major public events isn't the answer, noting that there aren't enough police officers in the entire state to line both sides of the marathon for all 26 miles of the race.
Instead, he said, reaching out to individual communities and members of the public is a smarter approach.
Davis said those engaging in criminal activity and those engaging in terrorist acts both cause problems for the larger community, even though they make up a tiny portion of its population.
"There is not magic bullet to deal with terrorism," Davis said. "I sincerely believe that the answer to this lies in community policing."
New Boston FBI head Vincent Lisi, who also spoke with Davis at the opening of the University of Massachusetts' new Center for Terrorism and Security Studies, said he took the same view.
Lisi said al-Qaida is constantly looking for new tactics and methods and has "exponentially increased the number of people who are going to come at us," making the fight against terrorism increasingly challenging.
While it's possible to screen passengers getting onto airplanes, Lisi said "there are no trip wires that are going to catch people buying pressure cookers" or other common items like fireworks, ball bearings or nails like those used in the marathon bombs.
Davis also said Tuesday that he was bracing for a possible third explosion in the minutes after two bombs ripped through the finish line of the marathon.
Davis said he knew immediately when he arrived on the scene that the twin explosions were terrorist acts - and he had been trained that al-Qaida hits in three attacks. Despite that danger, members of the bomb squad immediately began cutting into the bags left behind by those who fled the area in search of other bombs, Davis said.
The April 15 attack killed three people and wounded more than 260 others.
"Police agencies don't have the latitude to think that it's over. We are continually planning," Davis said, "We always plan for the worst and hope for the best."
Davis announced Monday he would step down after seven years on the job, saying it was time for a change for both him and the city. Davis, 57, said he was "leaning heavily" toward accepting a fellowship at Harvard University but was entertaining other offers as well.
University officials say the new center aims to become a leader in scientific research, education and training so it can better understand and respond to domestic and foreign security challenges.
Those challenges include terrorism, cyber-security, transnational crime and the threat of weapons of mass destruction.