BALTIMORE (WJZ)—Police make three arrests in the senseless murder of a 12-year-old boy, who was shot and killed while sitting on a front porch with three friends.

Mary Bubala has more on the story WJZ has been following for almost a year.

The murder of Sean Johnson in May of last year sent shockwaves across the city.

The 12-year-old was gunned down on the front porch of a Lake Clifton home as he watched the NBA playoffs with his friends.

WJZ investigated the murder of the seventh grade honors student, which went unsolved—with no witnesses coming forward – for almost a year.

But now police say multiple witnesses have identified three men as the attackers. Twenty-nine-year-old Danyae Robinson, 21-year-old Antwan Mosley and 18-year-old Derrick Brown are charged with Johnson’s murder.

Court records show Robinson served time in prison for attempted first-degree murder.

“Detectives identified individuals based on witness accounts. We’ve got some concerns for the safety of those witnesses, so their identities are being concealed,” said Anthony Guglielmi, police spokesman.

Court documents don’t reveal a motive for the shooting of Johnson and his friends—only that phone records were used to back witness accounts.

Just months ago, a WJZ investigation revealed Johnson’s murder was a tragic case of mistaken identity.  At the time, police told neighbors a gang targeting someone else just two streets away shot Johnson and his friends instead.

We spoke exclusively with Johnson’s mother.

“They said they were looking for other people in the neighborhood, and they thought that was them, and they just started firing,” Shawnta Little said.

Little says witness intimidation and Baltimore’s “Stop Snitching” culture prevent people from coming forward.

Police Commissioner Fred Bealefeld agreed.

“People know exactly who pulled the trigger,” Bealefeld said.

The two other suspects in the case had minor drug possession charges on their criminal records.

All three also face other charges of assault and attempted murder for the shooting of Johnson’s friends that night.