A man was filmed just after he allegedly attempted to abduct a 12-year-old girl as she walked to school.
The girl was grabbed around the waist and picked up on Old Run Road, Hunslet, Leeds, on 23 April, police said.
The West Yorkshire force said the man carried the child across the road to a secluded area, but she managed to fight him off and run away.
A passer-by disturbed the alleged attacker and took mobile phone video. CCTV video has also been released.
He ran off, but the woman contacted police and gave detectives her footage.
Det Insp James Entwistle said: “The circumstances of this incident are clearly very disturbing and we urgently need to identify the man shown in these images.
“The woman who intervened was able to film him on her phone as he ran off across a nearby park off Moor Road and we also have CCTV footage of him in the area which we are releasing.
“We believe the man is quite identifiable from these images and we would like to hear from anyone who recognises him or who has seen him in the area.”
The suspect is described as white, of medium height and build with short, dark hair and a beard.
He was wearing a blue hoodie, black T-shirt and beige trousers with black stripes down each leg.
Det Insp Entwistle said the girl had been left shocked and upset by the attack.