Pictures taken in the aftermath of the London Bridge terror attack show that a police bullet may have passed through a bus that was stopped nearby.
In the pictures, given to BBC News by an eye witness, the top deck of the bus appears to show a small hole in the glass at the front.
A separate photo also shows shattered glass at the back of the same bus, that was stopped near to where terrorist Usman Khan was shot and killed by armed police.
The eye witness, who asked not to be named, told the BBC that he dived to the floor when he saw and felt the impact of the back window smashing.
He said: "We are talking about a split-second of noise.
"In no more than a half-a-second I was on the floor.”
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Transport for London have already confirmed that a bus was damaged during the incident, while the Metropolitan police suggested the damage could have been the result of a ricochet from a police bullet.
Dr Rachel Bolton-King, associate professor of forensic science at Staffordshire University, told the BBC: "Ricochet bullets are often unstable once they have hit their first target surface.”
Cambridge students Jack Merritt and Saskia Jones were killed boy Khan in a knife attack at nearby Fishmongers’ Hall on 29 November.
Convicted killer and reformed prisoner John Crilly recently spoke of how he was “prepared to give his life” by tackling Khan - who be believed was wearing a live suicide vest - with a fire extinguisher.
An inquest into the incident opened last week and the Independent Office for Police Conduct is carrying out an investigation.