Inquiries into the shooting of a boy in the face and arms with a BB gun have revealed he was "playing a very dangerous game", police have said.
They were investigating reports that the 17-year-old was targeted while cycling in the Greenmeadow area.
But police said it transpired the boy had agreed to be shot by his friends.
They have arrested a 19-year-old man on suspicion of possession of an imitation firearm in a public place and cautioned him.
Ch Insp Keith Ewart said: "My officers spent a great deal of time and effort to investigate what was reported as a vicious attack by an unknown offender.
"However, we have discovered that these young men were actually playing a very dangerous game in which they thought it would be fun to see what happened if they shot one of their friends, who went along with the idea.
"BB guns are not toys and should not be treated as such. It is only by sheer luck that no-one else was hurt and the 'victim' didn't suffer any more serious injury.
"We hope that this will deter others from such stupidity."