The brothers suspected of the Boston Marathon bombings originally planned to carry out the attack on July 4 this year, a law enforcement official has said.
But the official claimed the Tsarnaev brothers decided to strike earlier because they completed building their bombs more quickly than expected.
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The so-called Islamic State released a statement alleging they had shot down a US warplane over Iraq.
The tree, which suffered previous wind damage in 2011, was made famous through the classic 1994 jailbreak film starring Morgan Freeman.
The British Muslim convert insisted he is not "currently" a fighter in Syria.