It had been a quiet afternoon in central London and Melville was taking pictures around parliament for stories about Britain's exit from the European Union.
Melville was standing below the bridge on the south bank of the River Thames opposite the Houses of Parliament at around 2:30 pm when the man landed near him.
"There was a lot of blood coming from his head. I thought this must be a domestic or horrible accident," Melville said.
"The noisiest part I can remember is the initial thud which I'm sure was the shock in my mind of hearing the bloke landing behind me. It was relatively quiet, in my mind anyway," he said.
Melville immediately phoned the emergency services and decided to go to nearby St Thomas's Hospital to alert doctors about the injured man. He climbed the steps to reach the bridge above, and that's when he saw other injured women lying on the pavement.
"At which point I thought this looks like it's more than someone's fallen over the wall," he said. Other bystanders were already rushing to help the victims. At the top of the bridge he began taking pictures.
"Of a dozen or so people, some of them seemed to be conscious. I didn't know there had been a vehicle involved at the time, someone said 'bus', someone said 'car' someone said 'shooting'," he said.
"It was just surreal and it was a fairly quick computation that this was a serious incident and a lot of people injured."
(Writing by Michael Holden; Editing by Guy Faulconbridge, Simon Robinson, Alessandra Galloni and Peter Graff)
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)