Why did Boston bomber hate the US?
5 August 2013 Last updated at 06:11 BST
One of the brothers suspected of carrying out the Boston bombings subscribed to radical right wing American literature about guns, government conspiracy theories and white supremacy.
The BBC's Panorama programme has learnt that Tamerlan Tsarnaev was reading right wing material before the attack.
It could challenge the perception of the brothers as straightforward radical jihadists.
Hilary Andersson reports.