Boston Police Commissioner Ed Davis recounted the law enforcement response to the Boston Marathon bombing and manhunt and recognized several officers involved in the Watertown gun battle at the IACP Conference Tuesday.

Commissioner Davis, who is retiring later this year, said the agency used crowd-sourcing to gather photos, video, and other evidence from the April 15 bombings at the Boston Marathon finish line. The bombing left three dead and 281 injured as local, state, and federal law enforcement officers initially created a 12-block perimeter around the wide-ranging crime scene.

"We all knew it was terror related," Commissioner Davis told a packed conference hall. "The crime scene was extensive."

The agency's use of social media also played an important part of the Boston PD's response to the incident. The agency put out only confirmed information that didn't compromise the investigation, Commissioner Davis said.

Davis also credited Boston medical personnel with responding rapidly with tourniquets and other trauma care during the incident.