A witness told how undercover cops swooped to arrest a stabbing suspect near Edinburgh Castle .
The 24-year-old witness was walking with friends from Princes Street when back-up officers in marked vans and cars came screaming past them to Castle Terrace car park where the incident happened.
Plain clothes officers were already on the scene and found a 'weapon' on the suspect before placing it in an evidence bag.
As a result of the incident a 29-year-man died at the scene.
Police said another man has been arrested in connection with the incident.
The witness said: "We were just walking home and we saw the police grab a man and take something off him.
"I'm not sure what it was but they took it out of the back of his coat or trousers and put it into a brown bag.
"He was being held on the ground by three officers.
"About three police vans came past with their sirens on the more from the other end of the road."
Another person who saw the arrest said: "There's a lot of police cars and they've closed off the road.
"We went over to see what was going on but the police weren't saying anything."
Following the incident cops attempted to reassure the public over the death.
A Police Scotland statement said: "Police in Edinburgh were called to Johnston Terrace at around 1.50pm today (Thursday 30 May) following a report of a disturbance.
"Emergency services attended and a man, in his twenties, was pronounced dead by the Scottish Ambulance Service.
"A man has been arrested in connection with this incident and officers remain at the scene."
Police Scotland Chief Inspector David Robertson said: "I would like to reassure local residents and businesses that there is not believed to be any ongoing risk to the public.
"Johnston Terrace and King's Stables Road are currently closed and people are asked to avoid the area, where possible.
"Our inquiries continue and anyone who may have witnessed this and has not yet spoken to officers should contact Police Scotland via 101, quoting incident 1876 of May 30, immediately."
