The shocking slaying of 18-year-old AmeriCorps volunteer Joseph Massenburg last year in the West Carrollton neighborhood was the work of three alleged members of a violent street gang known as the “Mid-City Killers,” according to a grand jury indictment this week that raised the stakes in the case.

Two of the men had been previously charged in the April 2013 killing on Eagle Street that authorities have described as a case of mistaken identity.

Massenburg, a recent high school graduate, had come to New Orleans less than three weeks before his killing to work for AmeriCorps, a national service agency.

Indicted this week were Glen “G Three Stone” Emerson, 19; Dwayne Miller, 23; and Richard “Trey” Ward, 17.

The five-count indictment also accuses them of murdering Ricky Johnson a few months later just a block away from Massenburg’s killing and of trying to kill Norman Watson on June 21, 2013, the same day Johnson was shot dead.

It further accuses the three men of a conspiracy to kill Dejuan “Baby Ross” Williams, who apparently was the target when Massenburg was killed on April Fool’s Day.

The indictment includes numerous gang enhancement charges that would mean additional decades behind bars if the men are convicted. All three are accused of committing the violent crimes to benefit a street gang whose main purposes were dealing drugs and committing murders, according to the indictment.

Massenburg, of Illinois, got caught in the middle of a bloody feud between the Mid-City Killers, or MCK, and a Carrollton-based gang called the Hot Glocks, according to reports.

Authorities first connected the killing to the MCK gang more than a year ago.

They arrested Emerson and linked him to Massenburg’s killing based on an anonymous tip from their investigation into the killing of Johnson, 33, who was slain in the 1400 block of Eagle Street.

Inside the apartment where police found Emerson, they also found a loaded Glock 9 mm pistol and a .32-caliber revolver. They found Miller there, too.

Emerson tried to escape through a window before police captured him. At the time, police said they didn’t believe he was the triggerman in either slaying.

The indictment Wednesday was handed up by a special grand jury impaneled to handle gang-related cases being pursued by District Attorney Leon Cannizzaro’s office, which has prosecuted several cases under a state racketeering statute that Cannizzaro claims he was the first in the state to exploit.

Many of the recent indictments have come as a result of investigations by a multiple-agency gang unit set up by Mayor Mitch Landrieu’s office that includes federal law enforcement.

The indictment handed up this week does not include gang racketeering charges, although it suggests a mounting focus on the Mid-City Killers.

Massenburg died at the hospital shortly after his shooting. At the time, police believed Emerson was the driver of an SUV used in the killing.

Authorities believe the men had been gunning for “Baby Ross” Williams, who has since been indicted along with purported members of the “110’ers” gang from the St. Thomas area in a 2012 killing on Annunciation Street — suggesting the type of cross-pollination that authorities say typifies New Orleans street gang activity.

Emerson, Miller and Ward all remained in Orleans Parish Prison late Friday. Criminal District Court Judge Karen Herman set bond for each at $3.5 million.

In a separate gang-related case, a prosecutor announced in Herman’s courtroom Friday that Cannizzaro’s office would not pursue the death penalty against four men who were indicted on first-degree murder charges last week in the slaying of 11-year-old Arabian Gayles last year in a Labor Day shooting that injured two others and outraged the city. She was shot on Gen. Ogden Street, near the Jefferson Parish line.

Interim Police Superintendent Michael Harrison blamed Gayles’ shooting on one gang “trying to rob the other one in a drug deal gone bad.”

That indictment names six people. The four accused of murdering Gayles are Chris Arana, Terry “T-Skinny” Green, Jermain Scott and Jacshaun “Ruger” Griffin; all are under 21. Authorities pegged Arana as a member of the “Breadwinners (M-Unit)” gang. Griffin, Green and Scott are fingered as MMG gang members.

M-Unit is believed to be an offshoot of the Hot Glocks.

Follow John Simerman on Twitter, @johnsimerman.