Davis says this year's race had a stronger security presence than usual:

We review each one of these events. At the end of our review last year, we determined that the crowds were larger than usual. And so we put additional officers at the end of the race," the police commissioner says.

There was no specific threat about this event ... this was a standard threat picture.

Davis says undercover officers were "fully deployed" among the crowd as were bomb-sniffing dogs.

DesLauriers declines to address a question about a circuit board reportedly found around the attack site. "That was brought up by a member of the media, not by me," the FBI agent says.

He's asked about the third, as-yet unidentified fatality. "There has not been enough work done to make a notification to the next of kin on the third victim," DesLauriers says.