Detectives and social workers have been investigating "appalling" footage posted on the YouTube website showing two young boys fighting each other.
The children, aged between 10 and 12, exchange punches, kicks and headbutts as a man filming the attack goads them into becoming more violent.
Police appealed for information to identify the two boys and the amateur film-maker, who is heard snigge
ring behind the camera as the pair fight.
During one section, one of the boys looks into the camera and asks: "Kicking is allowed, isn't it?"
And one of the boys shouts "He's crying" after punching the second child in the face.
The video, entitled Lethal Fight (Crawley), is believed to have been shot in a bedroom in the West Sussex town and posted on YouTube five days ago.
A second video, called Lethal Fight 2, was also posted on the video-sharing website and is believed to involve the same two boys fighting in the same room.
Sussex Police were alerted to the videos, which have since been removed from YouTube, by the Brighton Argus newspaper, which offered a £1,000 reward for a successful prosecution.
The police child protection team appealed for information leading to the identification of all three people in the videos.
Detective Sergeant Richard Harris said: "This appears to be a case of child cruelty and criminal behaviour by any adult involved in the making of this appalling video.
"Sussex Police child protection team and West Sussex young persons' services team will be working together to safeguard the welfare of the children and prosecute any adults involved in criminal behaviour."
A spokesman for West Sussex County Council said: "The (videos) will be forwarded to the appropriate child care team to see if the children in the films are known to us.
"The welfare of children is paramount to our children and young people's services and if they are known to us, we will take whatever action is appropriate."
YouTube said it would co-operate with any police inquiry.
A YouTube spokesman said: "YouTube is a community site used by millions of people in very positive ways.
"Sadly, as with any form of communication, there is a tiny minority of people who try to break the rules.
"On YouTube, these rules prohibit content like pornography or gratuitous violence.
"When people see content that they think is inappropriate they can flag it and our staff then review it."
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