BOSTON (AP) -- Boston Police Commissioner Ed Davis says he knew within seconds of the bomb blasts at the Boston Marathon that video surveillance would play a critical role in the investigation.

Davis told WFXT-TV today that surveillance video was pulled within 15 minutes of the explosions on Patriots' Day that killed three people and injured more than 180. It was images of the suspects that led to their identification.

He says he knew the bombs were "sophisticated, powerful" as soon as he arrived at the scene and saw the carnage, including two bodies and body parts strewn about outside a restaurant.

He says the investigation was a model of inter-agency cooperation, as Boston Police, state police and the FBI worked smoothly together.

He described being in "a combat type situation."