Police are looking for a man who stabbed another man at an out-of-control party in Piara Waters last night.
A 19-year-old Canning Vale man was taken to Royal Perth Hospital after being stabbed when he went to collect his younger brother from the party.
About 40 police officers, including mounted police, the canine section and the police helicopter were called to control the party on Southampton Drive at 9pm.
An estimated 500 people - primarily teenagers - were at the party, which had been advertised on social media.
As a St John Ambulance was attempting to drive through the crowd to attend to the stabbing victim its side window was smashed.
The 15-year-old accused of smashing the window is also alleged to have thrown items at police vehicles and horses.
He has been charged with assaulting a public officer, unlawful assembly and criminal damage.
Six other people were arrested by police.
A 26-year-old man, a 19-year-old man, an 18-year-old man, a 17-year-old boy and two 16-year-old boys will face charges in relation to unlawful assembly.
A small front-end loader was brought in to move glass and bricks from the site this morning.