Mayor Mitch Landrieu was among those in a packed courtroom Tuesday as a judge handed life prison terms to three young New Orleans men convicted in the gangland slayings of 5-year-old Briana Allen and a passing driver, Shawanna Pierce, during a 2012 attack in Central City that starkly dramatized the city’s epidemic of deadly violence.

The life sentences that Criminal District Court Judge Tracey Flemings-Davillier gave to Sam “Lil” Newman, Demond “Lil D” Sandifer and Tyron “T-Man” Harden were mandatory, following their February convictions in the two killings and other crimes.

Newman and Sandifer, half-brothers and members of the notorious St. Thomas-area 110’ers gang, also were convicted on gang conspiracy charges.

Legally the judge was required to weigh whether Newman and Sandifer could ever have a chance at parole, for both were juveniles when Allen and Pierce were slain. But the judge already made that call last year, refusing to grant either man the possibility of parole after separate juries convicted them in other killings.

Newman, 20, was found guilty of killing 22-year-old Jonathan “Kruga” Lewis in Gentilly less than two weeks after Briana and Pierce were fatally shot.

Sandifer, 20, was convicted a few months earlier in the 2011 slaying of 22-year-old Milton Davis.

Flemings-Davillier rejected defense attorneys’ pleas that their clients be shown mercy, following tearful testimony from members of both victims’ families.

Laura Pierce, Shawanna’s sister, read letters written by the oldest of the slain woman’s three boys, now 12 and 10. Then she stared down at Harden, who prosecutors say fired the AK-47 bullet that tore into Shawanna Pierce’s face as she drove through the neighorhood, killing her instantly.

“You probably didn’t mean to take my sister away but you did. That bullet traveled 3 1/2 blocks and struck her right here,” Laura Pierce said, pointing to her cheek. “And it went up into her head...Blood scattered everywhere. I feel bad for you cuz you don’t know what you’ve done. I see you looking right now with that look on your face. You’re going to realize it 10 years from know, 20 years from know, 30 years from now. You don’t realize the hurt you put in my heart.”

Pierce then turned to Sandifer, his head tilted, mouth and eyes open.

“Hopefully, I can forgive you for what you’ve done, but right now I do not,” she said. “You’ve shown no remorse. You slept during the trial. You didn’t care. It don’t matter, long as people send you money and girls holla at you. This is the life you choose, and this is the way you’ve been brought up. I feel sorry for you.”

Family members agreed that Newman flexed some remorse at trial, turning away as Pierce’s mother testified. On Monday, Sandifer and Newman, both serving life sentences, were hushed by a bailiff as they traded comments while Harden sat for a hearing on his motion for a new trial, which the judge rejected.

Harden argued mainly that a jury’s acquittal of him on the main racketeering charge from the indictment proved that his conviction was tainted by weeks of evidence against the 110’ers.

Assistant District Attorney Alex Calenda said it was never a secret that authorities believed Harden belonged to another gang, the Young Mafia Fellaz of the 7th Ward, but jumped in a car with Newman, Sandifer and Stanton “Na Na” Guillory on May 29, 2012. Calenda said the state racketeering statute invites crimes committed “in furtherance” of a conspiracy.

Authorities say the four were armed with the AK-47 and other firepower, setting out to attack Central City’s Young Melph Mafia, named for their stomping grounds around the former Melpomene public housing project, prosecutors said.

Among the members of that gang was Lionel “Lott” Allen, a relative of Briana. Authorities said he was among the intended targets hanging out on the neutral ground in the 1200 block of Simon Bolivar Avenue as the rival gang members opened fire about 6 p.m.

Briana took a bullet while celebrating her cousin’s 10th birthday on the porch of her great-grandmother’s house. Pierce, 33, was driving through the area when a bullet from an AK-47 struck her in the head. She died instantly.

Sandifer and Newman returned to New Orleans from the State Penitentiary at Angola for the sentencing.

Harden, 21, recently picked up a new charge: striking a female Orleans Parish sheriff’s deputy last month inside the city’s new jail. He wore a red “maximum security” jail jumpsuit to court Tuesday, rocking back and forth at the defense table.

After a three-week trial, the jury convicted Harden in the killings but not on the main racketeering count.

Guillory, the suspected driver, still awaits trial in the slayings and on racketeering and other charges from a 51-count indictment returned in May 2013.

The indictment named 15 alleged 110’ers and associates in a conspiracy, wrapping together 15 killings, numerous attempted murders, armed robberies and other crimes.

Along with the killings of Briana and Pierce, the jury convicted Newman in the murder of Marlon Smith and the attempted murder of Kevon Robinson on June 14, 2012, two weeks after the Central City gunfire.

Most of the 12 other defendants in the 110’ers racketeering case have since pleaded guilty, and several testified against Newman, Sandifer and Harden at their trial.

Police Superintendent Michael Harrison sat alongside Landrieu in the front row of the courtroom gallery for Tuesday’s hearing.

“The 110’ers were a human wrecking ball,” Landrieu said later. “The amount of pain and anger it causes to the family and community is just unbearable. A 5-year-old girl has her guts blown out on her grandmother’s porch. It’s not too harsh a statement to say those are acts of domestic terrorism.”

Absent in the courtroom was Burnell “Baldy” Allen, Briana’s father, who cradled his daughter in his arms as she lay dying. He is now serving a life sentence, having been convicted a year ago, along with two cousins, for what prosecutors described as a family-run drug business based at the house where Briana was killed.

Briana’s mother, Formeka Pollard, wrote a note that Calenda read in the courtroom because Pollard couldn’t stand to speak.

“I miss talking to her, holding her. She’s my only daughter, the one I long for; now she’s gone and she’s never coming back. She was too young to die,” the statement read. “At this moment, my heart is heavily racing in a rage, not out of anger but because not only have I lost my daughter’s life, your family will lose you as well. The only difference is that they can talk to you and see you.”

She went on: “The hardest part of all is that I have to sit here and face my daughter’s killers. If you have any blood that runs through your heart, any remorse for the pain you’ve caused to me as a mother, speak now.”

The convicted killers remained silent.

Follow John Simerman on Twitter, @johnsimerman.