Wolf Blitzer delivers the most important news and political stories of the day. Tune to The Situation Room weekdays 5-6:30pm ET on CNN.
The FBI released photos and video of two suspects in the Boston Marathon terror attack and are asking the public for help identifying them.
If you have any tips for the FBI, call 1-800-CALL-FBI or go to bostonmarathontips.fbi.gov.
RELATED STORY: FBI releases photos, video of Boston bomb suspects
SEE ALSO: Photos: Boston bombing suspects
Dr. David King had finished running the Boston Marathon when the bombs went off, and he rushed to the hospital to help.
CNN's Chris Lawrence takes a look at how investigators are piecing together clues in the Boston Marathon bombings.
RELATED STORY: Healing in Boston as investigators seek 2 seen near bombing