The Lafayette judge who sentenced Seth Fontenot on Wednesday to 13 months in jail for killing 15-year-old Austin Rivault and wounding two other teens said the sentence was appropriate for one of the toughest cases he’s ever presided over in 23 years on the bench.

Judge Ed Rubin said the 13-month sentence was a reflection of what the jury found in March, that Fontenot did not intend to kill Austin Rivault. He also said psychologists’ testimony in the March trial convinced him that Fontenot’s 18-year-old brain was not fully mature when he pulled the trigger.

The sentence outraged Rivault’s family, which had asked Rubin to send Fontenot to prison for 40 years, the maximum penalty for manslaughter in Louisiana. The sentence was meted out after more than two hours of often tearful testimony.

“I have never known a deeper aching sorrow,” Renee Rivault, Austin’s mother, said in describing her emotional state in the “879 days” since her youngest son was killed Feb. 10, 2013.

“Seth Fontenot, you have forever changed our family. … Daily, I am slapped in the face with the fact that my son is no longer alive. … My child, my baby,” she said through tears.

Austin’s family and friends Wednesday described a happy boy with a slight build, one who loved to fish and shoot skeet. His father described his youngest as a determined young man but one who now would never know the love of a wife or children.

Renee Rivault, as her husband Kevin and daughter Amanda did, asked Rubin to sentence Fontenot to 40 years.

As he did at the March trial, Fontenot on Wednesday said he feels “like a monster.” He also said he would “dedicate” his life “in the honor of Austin.”

“I sincerely apologize with all my being,” he said. “There’s not a day or moment that goes by that I don’t realize what I’ve done.”

Rubin’s sentence was met with joy on the Fontenot side of the filled courtroom and consternation on the Rivault side.

“Unbelievable,” Kevin Rivault, Austin’s father, said, shaking his head as he filed out of the courtroom with family and friends.

At Fontenot’s trial in March on charges of first-degree murder and two counts of attempted first-degree murder, a jury 11-1 found Fontenot guilty of the lesser crimes of manslaughter and aggravated battery. On Wednesday, Rubin decided on the lighter side of manslaughter’s zero-to 40-year prison range and sentenced Fontenot to three years at hard labor, then suspended all but 13 months of the sentence.

Fontenot, 21, also faced up to 10 years in prison for each of the aggravated battery convictions, and Rubin meted out a familiar sentence for each: three years at hard labor with all but 13 months suspended. Rubin ordered that Fontenot serve all three sentences concurrently, meaning he won’t spend additional time in jail for the crimes.

J.N. Prather Jr., the lead prosecutor, said the 15th District Attorney’s Office would appeal the sentence, which he described as too lenient, “totally inappropriate,” and in harsher terms.

“This is clearly an illegal sentence,” Prather said outside the courthouse.

Louisiana law states a violent offender must serve 85 percent of a sentence. Prather said Rubin didn’t say at the sentencing that Fontenot’s crime was one of violence and that Fontenot could be out in as a few as four months.

Fontenot’s attorney Thomas Guilbeau, who gave the Fontenot side of the filled courtroom a thumbs-up after the sentence was announced, said it was a just sentence for a young man who didn’t mean to kill anyone.

“He made an idiotic, stupid move and shot at a truck,” Guilbeau said. “He’s an 18-year-old, and 18-year-olds don’t think like adults.”

About 1:45 a.m. Feb. 10, 2013, Fontenot grabbed his 9 mm Beretta and ran outside his family’s Green Meadow Road home in south Lafayette, where his truck had been broken into before.

He fired three times at a Chevrolet Silverado he believed was carrying thieves who had tried to break into his truck. Fontenot testified in March that he shot once at the truck’s left front tire, then twice at the tailgate as the truck pulled away toward Johnston Street. Fontenot said he fired the shots to scare whoever was inside the truck, that he never meant to kill anyone, that it was a tragic accident.

Austin Rivault was hit in the back of his head and died in the Silverado’s rear seat. The 15-year-old driver, Cole Kelley, was shot in the leg, and passenger William Bellamy suffered a bullet to the back of his neck. Kelley and Bellamy survived to testify at Fontenot’s trial. And on Wednesday, both heard Rubin sentence Fontenot.

“Y’all can clap now,” an irate Kelley, 17, told Fontenot supporters as he walked out.

“Y’all can come see me,” he told them before an adult shepherded the 6-foot, 7-inch teen out the courtroom door. Later Wednesday, Kelley tweeted “The Louisiana judicial system is a joke.”

Fontenot, smiling and relieved after Rubin’s decision, was handcuffed and whisked off by deputies. Guilbeau said he could be processed for the state Department of Corrections in Allen Parish, and that Fontenot would not be sent to the Louisiana State Penitentiary at Angola.

Fontenot is scheduled to be back before a Lafayette judge in October in a drug distribution case that could eventually net him a longer sentence than he received in the Rivault killing.

A pretrial hearing is scheduled for Oct. 1 in Judge Jules Edwards’ court on two felony amphetamine distribution charges, which the District Attorney’s Office leveled at him in 2013 after the grand jury’s murder charges. The drug case has progressed slowly. According to Louisiana law, a conviction of one count of Schedule II drug distribution is two to 30 years in prison and a fine up to $50,000.

The Fontenot murder case has been closely followed in Lafayette and elsewhere. And Judge Rubin received hundreds of letters from Fontenot supporters asking for a lenient sentence, as well as from supporters of the Rivault family seeking the opposite.

Two of the letters were from jurors at Fontenot’s murder trial. Both asked Rubin for leniency.

“I do not feel that ‘intent’ was proven in this case,” wrote Deborah (Ginger) Pierret, who with 10 other jurors elected to convict Fontenot of manslaughter and aggravated battery instead of murder and attempted murder.

“I firmly believe that it was four kids who all had some responsibility for the situation and everything that could go wrong did — catastrophically,” Pierret wrote. She said her “heart truly hurts” for the Rivault family’s “sense of loss.

“However, I do not feel that a harsh, long-term sentence for Seth will change that in any way,” she wrote.

Tammy Philipp Leger was the lone juror who voted not guilty on all charges in Fontenot’s trial in March. She said she and other jurors would have found Fontenot guilty of a charge less serious than manslaughter if they had been allowed to.

“I believe and many on the jury believed it was an accident. … I believe Seth needs a sentence, but not a long one, I implore you to consider leniency and give him 5 or less years,” Leger wrote.