Three teenagers and one man all high on synthetic marijuana used big pieces of driftwood and concrete to savagely beat to death 15-year-old Brandon Augusta after an old argument re-erupted among the friends, authorities said Wednesday.

Marcus Ester, 21, and Tyrell Williams, 18, were booked into Ascension Parish jail Tuesday, each on one count of first-degree murder in the August slaying of the Donaldsonville teen, Sheriff Jeff Wiley said at a news conference Wednesday.

The two juveniles, who were not identified, one 16 and the other 17, were being transported Wednesday from a Monroe juvenile detention center to Ascension Parish, where they also will be booked in the boy’s death, Wiley said.

“His body was violated, and for 10 months, these individuals went about their business and enjoyed life,” Wiley said.

Brandon, a student at Donaldsonville High School, was last seen on the evening of Aug. 9 when he was with a group of friends. He was reported missing the following morning.

His body was discovered four days later on the Mississippi River levee.

On Monday, the Sheriff’s Office received a tip that led them to “a young man” who was able to tell detectives about the events of Aug. 9 that ended in Brandon’s death, Wiley said.

He did not identify the person who provided the information that led to the arrests.

“The mistake Brandon made, as a fine young man, was that he made a decision on a particular night to be with a certain group of people and take a drug, Mojo,” Wiley said, referring to synthetic marijuana. “On Aug. 9, across the levee from Donaldsonville, our victim, young Brandon, was with ‘his boys.’ ” Wiley said. “That’s what 15-year-olds do.”

At some point that night, Wiley said, “Brandon and another fellow resurrected a bad blood issue” about a fight between the two some weeks earlier.

Under the influence of the synthetic marijuana, the fight escalated quickly and Brandon was beaten to death, Wiley said.

“This was a bludgeon murder. There were several weapons of opportunity — big pieces of driftwood, big pieces of concrete” that were used to kill Brandon, Wiley said.

The teenager died of blunt-force injuries to his head, but the four “friends” continued to beat the boy’s body savagely after he was dead, the sheriff said.

“It’s an upsetting case. It’s one you don’t get over,” he said.

The Sheriff’s Office has asked the district attorney to begin the process of asking the 23rd Judicial District Court to order the two juveniles be tried as adults on first-degree murder charges, Wiley said.

The sheriff also said the two juveniles were in the Monroe detention center on crimes unrelated to Brandon’s death.

Brandon’s mother, grandmother, father and stepmother sat near the sheriff and listened intently as he explained at the news conference how the teenager died. At times, the mother and grandmother held hands and quietly cried.

Brandon had been raised by his grandmother in Donaldsonville, with his mother living next door. His father and stepmother live in White Castle.

“This is not a family of an at-risk kid who lived on the streets,” Wiley said. “He had a happy life and people who loved him.”

Brandon’s grandmother, Audrey Augusta, spoke briefly after Wiley.

Brandon, she said, “was a happy child, a compassionate child.”

“He was good with sports, good at drawing. He thought everyone was his friend, but not everyone was his friend,” Augusta said.

She said that she and Brandon had spoken on the Saturday he was last seen about going to church the following day. Brandon was supposed to call her about it on Sunday morning.

“He was a blessed young man. I’m grateful for my time with him,” she said.

Augusta said she had prayed that whoever had taken Brandon’s life would “tell the story.”

“My prayer was, ‘Lord, don’t let them rest, don’t let them sleep, let them toss and turn’ ” until they told someone about the crime, she said. She said she prays for the four involved.

Some people, Wiley said, may be under the impression that synthetic marijuana isn’t harmful, but the slaying of Brandon points to its true nature. “It’s the most dangerous drug we’re dealing with today,” he said.