(CNN) — Investigators have found explosives residue in the apartment that bombing suspect Tamerlan Tsarnaev shared with his wife and young daughter, a source briefed on the investigation said Friday.
The residue turned up in at least three places at the apartment in Cambridge, Massachusetts, the source said: the kitchen table, the kitchen sink and the bathtub.
U.S. law enforcement officials briefed on the progress of the investigation have provided CNN with other critical details:
– Tamerlan’s younger brother, Dzhokhar, told investigators that he and his brother built the devices in Tamerlan’s home;
– He also said the brothers originally planned a suicide attack on the city’s massive Independence Day celebration, which draws about 500,000 people and is televised nationally on CBS;
– Dzhokhar Tsarnaev also told investigators that he and Tamerlan chose to target the Boston Marathon only a day or two before the event. They changed their plans because their bombs were ready sooner than they expected.
The officials spoke on background because they were not authorized to speak with the media.