Investigators collected bullet casings from more than a dozen guns at the mass shooting scene in Brooklyn in which two people were killed and 28 others injured, according to a source with knowledge of the investigation.

Police haven’t released any details since a briefing Monday, when Acting Commissioner Richard Worley said in response to a question from a reporter that there were at least more than three guns fired and that the crime lab was working to determine how many.

Baltimore police have arrested a 17-year-old and charged him with being involved in a mass shooting at a crowded South Baltimore block party on Sunday.

Two people were killed in the shooting and dozens more were injured.

The unnamed person was taken into custody Friday morning around 7 a.m. after police searched a home. Detectives took the teen to Central Booking, where he is being charged with possession of a firearm by a minor, assault weapon possession, reckless endangerment and handgun in vehicle.

Police have not said whether the teen fired a weapon that injured people or fatally struck 18-year-old Aaliyah Gonzalez or 20-year-old Kylis Fagbemi. Officials say 28 people, most of whom were teenagers, were also injured in the attack — one of the largest casualty counts for a single incident in Baltimore’s recent memory.