Detectives investigating a fight at a party in Warminster which left one boy with a stab wound and another with a broken jaw, are asking for the help of parents.
Police attended reports of a disorder outside Chapmanslade Village Hall at around midnight on Saturday 28 September.
A 15 year old boy has been arrested on suspicion of Grievous Bodily Harm and is in police custody.
Det Insp Tom Straker, from Wiltshire Police, said: "This was a fight between individuals from the party who knew each other.
"It was not a minor incident, a knife was used to stab one victim and the other was hit so hard that his jaw was broken.
"We are sure that the community will agree that this cannot be tolerated, we need the support of parents/guardians to encourage those attending the party to talk to police about what they saw and heard.
"We also believe that there are photos and video of the incident which could be vital to our investigation so I need parents to check mobile phones.
"I must stress that we need witnesses to come forward, they are not in any trouble and will be dealt with sensitively. If anyone has worries about telling us what they know please call us and we can help reassure them."
Inspector Andy Fee, Inspector for West Wiltshire CPT said: 'This was a serious incident involving young people. We will be increasing out patrols to reassure the local community of Chapmanslade.'
Anyone with information should call DC James Fry at Melksham CID on 101 at Melksham CID on 101.
Alternatively you can call Crimestoppers anonymously on 0800 555 111.