Richard Jones, who had stepped off a bus just before it was blown up in Tavistock Square, told the BBC he saw an agitated man fiddling suspiciously with a paper sack on the bus.
"He was standing next to me with a bag at his feet and he kept dipping into this bag and fiddling about with something," Jones said. "I was getting quite annoyed with this because it was a crowded bus. Everybody is standing face-to-face and this guy kept dipping into this bag."
Two people died on the bus, which was bombed about the time three subway trains were hit. The overall death toll form the attacks reached 50 Friday.
Notable deaths of 2014 [PHOTOS]