Two more people, including a 15-year-old boy, have been charged in connection with the deadly shooting that broke out in a crowd of roughly one million people gathered last month to celebrate the Kansas City Chiefs Super Bowl victory, Missouri prosecutors announced Thursday.

The teenager was charged with unlawful use of a weapon and armed criminal action and is detained at the Juvenile Detention Center, the Office of the Juvenile Officer in Missouri judicial court’s family court division said. A certification hearing will be held to determine whether the teen should stand trial as an adult. 

One man, 20-year-old Terry Young, was charged on Thursday with second-degree murder, unlawful use of a weapon and two counts of armed criminal action, Jackson County Prosecutor Jean Peters Baker announced.

"We get complicated cases, but this case has been challenging," Bakers said, noting the grave impact of the shooting last month, as well as the scope of the police investigation.

She noted that everyone who fired shots that has been identified has been taken into custody, but additional charges are expected. Officials have previously said 12 people brandished firearms in the shooting and at least six of them fired shots. 

Before this week, authorities said two other men had been charged with murder, and two other juveniles were detained on "gun-related and resisting arrest charges."

The Super Bowl parade shooting is also the intense focus of federal officials who are trying to track every gun fired during the shooting fracas. Federal authorities said several guns were found on the ground after the shooting, and three men have been charged with federal firearms counts in connection to illegal guns used in the shooting. 

6 people now charged in Kansas City shooting

The shooting began around 2 p.m. on Feb. 14 as Chiefs fans gathered for the celebration in front of Kansas City's Union Station. More than 20 people ages 8-47 suffered gunshot wounds in the shooting. Lisa Lopez-Galvan, a mother of two and local DJ, was fatally shot.

The prosecutor's office said that surveillance video showed Young fired several shots after an argument broke out and one person pulled out a firearm.

Dominic M. Miller, 18, and Lyndell Mays, 23, were charged days after the shooting with second-degree murder, two counts of armed criminal action and unlawful use of a weapon. 

While all three adults are charged with murder, Baker said a bullet from Miller’s firearm fatally struck Lopez-Galvan. 

One witness said a group of people approached Mays and another person, and they “began arguing about why they were staring at each other,” Kansas City police detective Grant Spiking said in a probable cause statement. Mays allegedly admitted to shooting first and firing two shots, and he “acknowledged he shouldn’t have pulled a gun out," Spiking noted.

Second-degree murder is punishable in Missouri from 10 years up to life in prison. Prosecutors requested for Young to be held on a $1 million cash bond. 

Court records did not list an attorney for him.

Federal prosecutors probe guns used in shooting

As Missouri officials stack up charges against the assailants of last month’s assault, federal prosecutors are probing where the guns in question came from. So far, three Missouri men have been charged in U.S. District Court for illegal firearms trafficking and straw purchases tied to two weapons connected to the parade shooting.

"Stopping straw buyers and preventing illegal firearms trafficking is our first line of defense against gun violence," said U.S. Attorney Teresa Moore.

One gun that officers found after the shootout was bought by 22-year-old Fedo Antonia Manning from Frontier Justice in Lee’s Summit, Missouri, in 2022 and had been trafficked on the black market, according to court documents. Based on how the gun was found, officials said it could have fired several rounds before it was abandoned.

Manning allegedly trafficked dozens of firearms, court documents said, and 15 guns he had previously bought that law enforcement officers seized were in the hands of other people, including several who were legally banned from owning firearms.

According to another criminal complaint filed in U.S. District Court, Western District of Missouri, a Stag Arms 300-caliber pistol that authorities recovered after the shooting was purchased at a gun show in Kansas City in November.

Ronnel Dewayne Williams, Jr., 21, allegedly bought the firearm for Chaelyn Hendrick Groves, 19, who went with him to the gun show but was too young to buy it himself legally, court documents said.

Missouri has some of the most lenient gun control measures in the country, according to gun control advocacy and research group Giffords Law Center to Prevent Gun Violence. Since 2017, it has been legal for people to carry concealed, loaded guns without a permit or background check, according to Giffords.

Contributing: N’dea Yancey-Bragg, Cybele Mayes-Osterman, USA TODAY