Investigators are working hard to find out if the Boston bombing suspects had outside help and training on how to build their bombs.
A new government document obtained by ABC News said the Tsarnaev brothers used more than just bomb-making instructions found on a magazine.
The FBI has rebuilt the bombs and discovered toy remotes likely triggered the bombs.
Now investigators are trying to figure out what happened during Tamberlan Tsarnaev's six month trip to Russia. \