article_snippet: Authorities quickly identified the Boston bombing suspects, but almost immediately after Tamerlan Tsarnaev was killed during the manhunt for the perpetrators and Dzhokhar Tsarnaev was captured, investigators privately questioned if more people were involved.
article_snippet: If there were others, perhaps a bomb maker is on the loose.
article_snippet: The twin bombings in April 2013 killed three people and wounded more than 250 others.
article_snippet: There are other clues that the brothers would have needed help with the bombs.
article_snippet: Also, investigators apparently were troubled that investigators recovered one remote-controlled detonator at the scene of the bombings when there should have been two.
highlights_snippet: Investigators have always wondered if more people were involved in the bombings than just the brothers .
  