A bus driver has been stabbed in the centre of Sheffield and is in a serious condition in hospital.
Police were called to Arundel Gate at 13:50 BST after reports of a 40-year-old man being stabbed in the back and in the leg.
South Yorkshire Police said a 17-year-old boy had been arrested on suspicion of attempted murder.
First Bus thanked members of the public who helped the driver and detained the teenager at the scene.
Det Ch Insp Jamie Henderson, of South Yorkshire Police, said: “Thanks to quick-thinking actions of members of the public, the 17-year-old boy was detained at the scene until officers arrived.
“Their brave actions meant that we were able to take control of the situation quickly, get the offender into custody and the victim to hospital. I’d like to thank everyone who assisted.
“At this time, we believe this was an attempted robbery which has escalated, and officers are in the area carrying out inquiries to ascertain exactly what happened.”