CNN Starting Point May 2, 2013 11:03:00
Knew at the university of massachusetts dartmouth was involved with the boston marathon bombing. he has cooperated fully with the authorities and looks forward to the truth coming out. >> reporter: a month before the marathon tsarnaev told two of his friends over lunch that he knew how to make a bomb and according to the criminal complaint, one of those friends, the friend saw vaseline in his dorm room, he thought that it was used to make a bomb. we've been talking to experts and we're told that vaseline was likely used on the pressure cooker lid to prevent sparks which couldexplosives. >> how...