Source: Boston Marathon bombing suspects first had July 4 plot

BOSTON -- Bombing suspect Dzhokhar Tsarnaev and his older brother Tamerlan initially planned the attack for the upcoming July Fourth holiday but changed their minds shortly before the Boston Marathon because the race was an "ideal" target, a federal law enforcement source said Thursday.

Among the places they considered for their Independence Day bombings were the popular and always densely crowded evening fireworks spectacular on the Charles River Esplanade and at least one and maybe more Boston police stations, the source said.

It turned out the brothers' bomb-making skills led them to reconsider their entire plan, the source said. They assembled the two pressure-cooker bombs that exploded at the marathon April 15 quicker than expected so they trained their sights on the marathon instead, the source said. The bombings killed three and injured more than 260.

Information about the switch in targets came from several leads as well as details gleaned from hospital interviews with Dzhokhar Tsarnaev two weeks ago before he was read his Miranda rights and stopped talking to authorities, the source said.

The 19-year-old student at the University of Massachusetts Dartmouth told FBI agents he and Tamerlan Tsarnaev saw Patriots Day -- like July Fourth in Boston -- as an event with huge, festive crowds and loaded with patriotic symbolism, the source said, adding that they considered it an ideal time to set off the bombs. Turning the attack into a suicide bombing was also considered, Dzhokhar Tsarnaev told investigators, according to the source. But the brothers did not have suicide vests and took no actions that would have allowed them to actually detonate suicide bombs, the source said.

Dzhokhar Tsarnaev told investigators before they switched targets, he and his brother built their pressure-cooker bombs at Tamerlan Tsarnaev's home, according to the source. Once they settled on a day for the attack, they scouted the marathon course before deciding that the finish line -- crammed with onlookers and a large news media presence -- was where they would set off the bombs, the source said.

On Thursday, federal investigators also continued to search two laptop computers belonging to the Tsarnaev brothers for any evidence the pair had help planning the attacks, according to the law enforcement source. And Thursday night, Tamerlan Tsarnaev's body was claimed by a local funeral home, said Terrel Harris a spokesman for the Boston medical examiner's office.

Tuesday, attorneys for Katherine Russell, Tamerlan Tsarnaev's wife, said in a statement that her wish was that his remains be released to his family.

Tamerlan Tsarnaev died after an early morning shootout with police four days after the attacks at the end of a high-speed chase from the Cambridge campus of MIT to the Boston suburb of Watertown.

His computer, along with a laptop owned by Dzhokhar Tsarnaev, were recovered in the days after the bombing.

Investigators are poring over the computers' emails, pictures, contacts and other data that could expand the probe, including whether extremist Islamic leaders in Russia radicalized Tamerlan Tsarnaev, the source said.

Dzhokhar told investigators that he and his brother had listened to online sermons of Anwar al-Awlaki, the American-born radical who was killed in a 2011 U.S. airstrike in Yemen. Two college friends of Dzhokhar Tsarnaev were charged Thursday with trying to hide the laptop and a backpack after the bombings in an effort to conceal the 19-year-old's role in the attacks.

They were charged with willfully conspiring to commit an offense against the United States by destroying or concealing items to impede or influence a criminal investigation.

A third friend was charged with lying to federal investigators about the removal of the items. They are cooperating with authorities, the source said.