Police believe "a number of people" witnessed a double stabbing on a Bradford street and appealed for them to come forward.
West Yorkshire Police was called to Seymour Street, off Leeds Road, at about 22:15 BST on Sunday, where two men were found injured.
A 31-year-old man suffered serious injuries and remains in hospital, while another was treated for non life-threatening injuries and has since been discharged.
A 36-year-old man arrested on suspicion of attempted murder has been bailed by police pending further enquiries.
Det Ch Insp Tom Levitt said: "We would appeal to anyone who was in the Seymour Street/Mount Street area to come forward with information.
"We are keen to see any footage of the incident filmed on mobile phones and uploaded to Snapchat."
He added: "There were also a number of cars that drove past, so we would appeal to anyone who has dashcam footage to come forward."
West Yorkshire on BBC Sounds
