A teenager arrested in connection with the mass shooting at the Juneteenth celebration in Round Rock told police that he fired his 9 mm gun three times at a teenager, injuring him in the leg, according to an arrest affidavit.

Ricky Thompson III, 17, of Manor, was charged with aggravated assault with a deadly weapon. The charge is a second-degree felony punishable by up to 20 years in prison. Two people were killed and 14 others were injured in an altercation between two groups of people at the celebration on June 15 at Old Settlers Park. Police have declined to say what the argument was about.

Part of the argument was between Thompson and a 17-year-old male, according to the affidavit. It said Thompson pulled out his gun from his waistband during the altercation and shot at the victim, striking him once in the leg.

The affidavit did not provide details about the argument.

An officer providing security at the event found out that the victim had gone to St. David’s hospital for treatment for a gunshot wound, according to the affidavit.

Police have also arrested a second suspect in the shooting who is a juvenile and was taken to the Williamson County Juvenile Justice Center.

Round Rock Police Chief Allen Banks has said there was more than one shooter at the event, which authorities are continuing to investigate. The two innocent bystanders who were killed were Ara Dukes, a 54-year-old educational administrator from Pflugerville, and Lyndsey Vicknair, a 33-year-old lawyer and mother of three children.

This article originally appeared on Austin American-Statesman: Suspect said he shot teenager at Juneteenth event, police say