1:58 PM PT: According to MSNBC, investigators will play video of of the two men they are seeking from the scene of the attack. The press conference is scheduled to begin at 5:00 PM ET.
2:02 PM PT: Here's another stream. A press officer just said the video and photos will be posted on FBI.gov in "five to ten minutes."
2:06 PM PT: According to CBS, the FBI will be asking the public to help name the people in the videos. One man wears a white cap, and his actions led them to be interested in the second man.
2:06 PM PT: CBS's Scott Pelley says the men will be described as "suspects."
2:07 PM PT: There are two easels set up in the room. Presumably one easel for each man.
2:20 PM PT: After a long delay, the briefing is now getting underway.
2:22 PM PT: Richard DesLauriers, the FBI Special Agent in Charge, opens the briefing. "We initially developed a single person of interest," he says. But investigators still did not know if that person was working with any other individuals. Now, they think they have a second suspect.
2:22 PM PT: FBI.gov has images here. FBI is asking for public's health in identifying subjects.
2:23 PM PT: Here is a 30-second video posted by FBI:
2:25 PM PT:
2:27 PM PT: The FBI says these images are the only images that should be treated as credible. Suspect 2 with the white cap is the only one he says that he believes placed the device.