Baltimore Police arrested a 17-year-old Friday on firearm charges in connection to last weekend’s mass shooting that wounded 30 people, including two fatally, the same day sources said more than a dozen guns were fired at the scene.

Police recovered shell casings from at least 12 guns from the scene of the mass shooting, according to sources with knowledge of the investigation. It’s not known exactly how many shooters there were — one shooter could have used two guns, for example — or if all the shell casings were tied to the mass shooting at the Brooklyn Homes early Sunday morning.

Detective Freddie Talbert, a spokeswoman for the police department, said Friday afternoon that the teen’s arrest was the only one police had made so far but that there are “multiple” suspects.

Authorities said earlier this week that they believed there were at least two shooters in the 800 block of Gretna Court, where two people were killed and 28 people wounded. Aaliyah Gonzalez, 18, died at the scene and Kylis Fagbemi, 20, died at a hospital.

The teen’s attorney, Michael Clinkscale, said his client was one of the 30 shot during the annual “Brooklyn Day” block party in South Baltimore. Clinkscale said the teen was one of several people who were treated at an area hospital in the immediate aftermath.

“He was running away just like everyone else and he was shot,” Clinkscale said.

The teenager has not been charged with shooting anyone and authorities have not said if they believe he did.

The police department said the teen is being charged with possession of a firearm by a minor, assault weapon possession, reckless endangerment and having a handgun in a vehicle. He was arrested following a search warrant on a home, the agency said.

A video circulating around social media after the shooting shows a young person at the community celebration remove an assault-style weapon from his book bag and brandish it.

Clinkscale said police claim that his client is the person in the video. Asked whether the teen in the video was his client, he reiterated that there was “an allegation” that it was. As to the contents of the bookbag, the teen’s attorney said “there is an allegation that it was a gun, but we do not know.”

Police detectives believe the 17-year-old was “involved” in the mass shooting and, on social media, refer to him as a “person of interest.”

The investigation into what is likely Baltimore’s largest mass shooting is still open and ongoing.

[ What we know so far about the mass shooting at Brooklyn Homes in South Baltimore ]

Saturday’s Brooklyn Day block party was held near the 800 block of Gretna Court. What began as an intergenerational celebration, with food, a pony ride, face painting and music, turned into a crime scene shortly after 12:30 a.m. Sunday when shots broke out.

Baltimore Mayor Brandon Scott called the arrest Friday a “signal” that “with the community’s help we can get justice for Aaliyah, Kylis and everyone else who has been impacted by this tragedy.”

“Bringing the perpetrators of this horrific crime to justice is our number one priority, and I want to thank everyone who had a hand in bringing this person of interest in,” Scott said. “I am confident that this investigation will continue diligently working through every single tip, lead and suspect.”

Three shooting victims remain at local hospitals, with all of them in fair condition, police said Friday. The vast majority of those wounded were in their teens. Fifteen of them were under the age of 18.

Experts said this week that the size of the shooting could be a complicating factor for the investigation. It took place in a large crowd, meaning there could be dozens of witnesses and countless social media posts or other footage capturing key moments.

Another factor: Witness’s possible fear for their own safety, should they share information with police.

Erika Walker, the tenant council president of the public housing complex where the shooting took place, Brooklyn Homes, said people were fearful of retaliation.

“They’re scared, period,” she said.

There is a $28,000 reward for information that leads to an arrest and charges. The Metro Crime Stoppers tip line is 1-866-7LOCKUP. Callers can remain anonymous.