From BBC
Mr Whitby, told BBC News: "I was sitting on the train reading my paper.
"I heard a load of noise, people saying, 'Get out, get down'!
"I saw an Asian guy run onto the train hotly pursued by three plain-clothes police officers.
"One of them was carrying a black handgun - it looked like an automatic - they pushed him to the floor, bundled on top of him and unloaded five shots into him.
"I saw the gun being fired five times into the guy - he's dead."
Passenger Briony Coetsee said: "We were on the Tube and then we suddenly heard someone say, 'Get out, get out' and then we heard gunshots."
BBC radio has said Police have just confirmed it was a suspected suicide bomber.