Bullets that fatally struck two bystanders during a shootout at a Seattle food festival last weekend do not appear to have come from the gun that a 15-year-old arrested at the scene was firing, police said in court documents filed on Wednesday.

The teen sprayed an untraceable “ghost gun” into a crowd, authorities say. Preliminary ballistics testing did not match the bullets recovered from the deceased bystanders to that weapon.

Police have linked the shooting to gang violence. Shell casings found at the scene on Sunday indicate four weapons were fired.

“We have small groups that appear to be at odds with each other, and in our city 0.01% of the population is connected to 52% of our shootings,” Seattle police chief Shon Barnes said at a news conference on Monday.

A 19-year-old suspect was shot and killed at the scene. Police have been trying to identify at least one other person involved in the shooting. They have not indicated who might have fired the bullets that killed the bystanders.

In the crossfire, at least four other bystanders were wounded, including a two-year-old boy. Videos posted to social media showed a chaotic scene, with swarms of people running for safety as shots are heard in the distance.

The King county prosecutor’s office has charged the 15-year-old with first-degree assault with a firearm enhancement and unlawful possession of a handgun by someone under 18.

Prosecutors are seeking for his case to be moved to adult court. If convicted in juvenile court, he could face two and a half years in juvenile detention. In adult court, a conviction would come with a penalty of about eight to 10 years in prison, and another possible five years for the firearm enhancement.