A girl of about 14 used a knife to threaten a group of teenage girls.
She had already struck out with her fists at the three in Tilgate Park, Crawley.
The final stages of the Prom in the Park music festival were taking place nearby.
The girls were walking near the lake just after 11pm when the girl lashed out.
One of the injured girls had a black eye and the other two were slightly bruised.
The attacker was slim, with collar-length straight brown hair. She was wearing large hooped ear-rings, a short black skirt, and a dark top.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules hereComments are closed on this article