5:25pm ET: President Obama is headed to Boston on Thursday.
5:20pm ET: The FBI has stated the explosives were likely placed in a "black nylon bags," and found fragments of nails, BBs, and what may "possibly" be pressure-cooker(s) at the scene.
5:15pm ET: An official with the FBI announced this afternoon that there are no leads or motives at this time, and noone has stepped forward to claim responsibility, though the investigation is still in its "infancy." He asked for members of the public to come forward with any information, noting, "The person who did this is someone's friend, relative, or coworker...someone knows who did this."
4:50pm ET: A friendship between two rivals in the face of tragedy. "We stand united with the Red Sox," tweeted the Yankees on Tuesday. "Bigger than the game. Thank you!," replied the Boston baseball team's account.
4:45pm ET: An update on the victims taken to Boston Medical Center from WHDH-TV 7News.
4:36pm ET: The subject in one of the more iconic—if brutally graphic—photos from the Boston bombing aftermath has undergone surgery to amputate both legs, his father confirms to the AP, "because of extensive vascular and bone damage." The man was seen being wheeled away in a wheelchair with both legs seemingly gone below the shins. He was at the Marathon to cheer on his girlfriend—the wrong place at the wrong time, says the father.
4:22pm ET: The day after, national guards and police are armed with machine guns in downtown Boston.
3:45pm ET: Marathon runners and citizens of Boston have erected an impromptu memorial at the site of yesterday's blasts.
3:00pm ET: The second bombing victim has been identified as 29-year-old Krystle Campbell. Campbell was a native of Medford, Massachusetts, and a 2001 Medford High School graduate. No other information is known at this time, and the identity of the third person killed in the blast is still unknown. Eight-year-old Martin Richard of Dorchester, Massachusetts, was also killed in the attack.