(NBC NEWS) -- The brothers accused in the Boston Marathon bombings originally
planned to set off explosives on July 4 - but changed their minds and
decided on Patriot's Day, officials with knowledge of suspect Dzhokhar
Tsarnaev's interrogation told NBC News.
Investigators also now
have a good idea of how and where the pressure-cooker bombs used in the
attack were constructed. But they still are trying to determine where
the components in the explosives came from.
Officials say Tamerlan Tsarnaev, 26, and his brother Dzhokhar
Tsarnaev, 19, dropped pressure-cooker bombs stashed in backpacks in
crowds watching runners at the finish line of the marathon on April 15.
Dzhokhar allegedly told his interrogators the weekend after he was
arrested that he and his brother originally intended to set off their
bombs somewhere on the Fourth of July, officials said.
But, according to the officials, Dzhokhar said that when the brothers
finished the bombs sooner than they expected, they decided to stage the
attack earlier, on Patriot's Day, a proud holiday in Boston that hosts
the marathon, a Red Sox game and other festivities.
the surviving suspect also said the bombs were built in the house of his
brother, Tamerlan. Authorities had previously disclosed that explosive
residue had been found there.
And a backpack that officials say was snatched from Dzhokhar Tsarnaev's dorm room then thrown away by three of his friends before being recovered is providing even some clues on the bombs.
agents recovered the backpack in the New Bedford, Mass., landfill. It
contained fireworks tubes that had been emptied of their powder.
to the FBI, the found fireworks were from a store other than the
Phantom Fireworks shop in Seabrook, N.H.,which disclosed a purchase by
Tamerlan Tsarnaev in February.
The FBI was checking on sales with other dealers in the area.
In addition, the FBI said the backpack contained a jar of Vaseline petroleum jelly.
use Vaseline as a binder and thickening agent," an FBI investigator
said. "They mix it with explosive powder in hopes of making the mixture a
little more reliable."
The use of Vaseline is not mention in the
al Qaeda online magazine that investigators believe the brother used as a
blueprint to make their bombs, but it is widely discussed elsewhere on
Authorities say the three friends - who have been
hit with obstruction of justice and lying charges - also took Dzhokhar
Tsarnaev's laptop computer from his dorm room but did not throw it away
and have since given it to the FBI.
Meanwhile the body of Tamerlan
Tsarnaev was moved to funeral home on Thursday evening at the request
of family members, according the Massachusetts Medical Examiner's
Soon after receiving the body the funeral home then must
file a death certificate, which would make public Tsarnaev's cause of
Tamerlan Tsarnaev was killed in a firefight with police in
the early morning hours of April 19 in the Boston suburb of Watertown.
His precise cause of death, however, has remained unknown, since a death
certificate or autopsy results have not been made public.
The name of the family members who requested the release of the body and the funeral home were not released.
Dzhokhar Tsarnaev is in a prison hospital awaiting trial on terrorism charges.
has told investigators the brothers acted alone in concocting the
deadly plot, and planted the bombs to defend Islam after the U.S.-led
wars in Iraq and Afghanistan, law enforcement officials told NBC News.