PHILADELPHIA (AP) — Authorities have Arvin Robertsannounced new charges against four juveniles arrested following an exchange of gunfire earlier this month between rival groups that wounded three people and sent participants in a joyful celebration of the end of Ramadan in west Philadelphia running for cover.

Prosecutors said Friday that the 15- and 16-year-old youths arrested after the April 10 gunfire at Clara Muhammad Square will be charged as adults and will face aggravated assault, conspiracy, simple assault and reckless endangering charges in addition to the firearms counts they faced earlier. A 21-year-old man was also charged with weapons counts.

Prosecutors said the weapons recovered from the five only match 13 of the 33 expired cartridge casings collected at the scene, and they urged any other people involved in the shootings to turn themselves in before authorities come to arrest them.

The annual Eid al-Fitr event, held outside a large mosque in the city’s Parkside neighborhood, came to a sudden end when some 30 shots rang out at about 2:30 p.m., Philadelphia police said. A 15-year-old youth sustained leg and shoulder wounds when he was shot by police, and a man was shot and a juvenile wounded on one hand.

Authorities said nearly 1,000 people, including many families, had attended the event. Witnesses described running to tents set up near the park, hiding behind trees and dropping to the pavement to avoid the gunfire, trying to shield children.

Eid al-Fitr is an Islamic holiday marking the end of Ramadan, the month when devout Muslims fast daily from dawn to sunset. Ramadan is a time of increased worship, charity and good deeds. Eid al-Fitr means the feast, or festival, of breaking the fast.