A man who confronted a knife attacker on rollerblades as he stabbed people in Bristol feared a friend with him would be killed.
Gary Stancer - who initially thought the weapon was a toy - used a road sign to try to disarm the man, who was knifing pedestrians on Wells Road.
Avon and Somerset Police praised people who challenged the attacker before officers arrived, on Tuesday afternoon.
A 37 year-old man was arrested at the scene and taken to hospital.
Officers were called to the Wells Road in south Bristol, just after 15:00 GMT.
Mr Stancer said he reacted after seeing someone get stabbed in the back with what he initially thought was a toy.
When he realised the weapon was real, he and friend Rob chased the man onto nearby Redcatch Road, where he turned on them.
"I thought he was killing Rob," said Mr Stancer. "He got him in the leg and then stabbed him in the hand a couple of times.
"I picked up a road sign and attacked him with it."
Officers then arrived on the scene and arrested the suspect, who remains in hospital.
Three other people sustained knife wounds but police say none of them were seriously injured.
Police are keeping an open mind about the motive for the attacks, but praised people who challenged the man.
Ch Insp Nigel Colston said: "I'd like to thank those members of the public that gave us assistance, it made a tremendous difference to what happened."
He added there would be extra patrols in the area over the next few days to reassure people.
"We understand the concerns of the public. We do remind them that generally speaking this is a safe place," said Ch Insp Colston.