A Georgia sheriff has charged nine people with murder after a fight between two high school girls escalated into a neighborhood street brawl with a mob wielding baseball bats and knives — and one driver charging at people with a car — before a teenager was fatally stabbed in the neck.

“This is one of the most senseless murders that we’ve had,” Richmond County Sheriff Richard Roundtree said in a phone interview today. “Before this escalates and becomes the norm, we want to take a hard stance and say we are not going to tolerate this in our community.”

Demajhay Bell, 18, died at a hospital Sunday, two days after the sprawling fight in a subdivision just outside Augusta. The sheriff said the brawl was so chaotic that Bell, a bystander who stayed inside through most of the fighting, got stabbed by a friend trying to lash out at a combatant who had broken his arm with bat.

Investigators suspect say the deadly melee last Friday was actually sparked days earlier by a fight between two girls at Glen Hills High School. They were arguing “over a boy and some racy photos,” Roundtree said.

School officials stopped the fight on campus, but the dispute festered in social media posts and text messages, the sheriff said. Friends and relatives of each girl joined in and soon there were two groups threatening to settle the dispute in the streets.

“The brawl itself was a coordinated effort,” Roundtree said. “The group in the neighborhood knew the other group was coming to fight.”

Eyvette Byrd, the mother of one of the feuding girls, told deputies that between 30 and 50 people showed up at her home for the fight. According to the sheriff’s incident report, some had armed themselves with bats, pipes and knives. Byrd was among those later arrested on assault and murder charges.

Video posted online of the brawl shows two young women in a fistfight in the street while bystanders circle them. A couple of young men are holding baseball bats. One uses his bat to whack the hood of a Dodge Charger, which lurches after him and plows into someone’s front lawn. Another young man in the street gets cracked in the arm with a bat.

The two-minute video ends with bystanders suddenly screaming, “Call 911!” A person runs past the camera with a hand clutched to his neck, where there’s a large blur of red.

It wasn’t clear who took the video, but the sheriff confirmed it was authentic and that the person clutching his neck was Bell.

“He was not even participating,” said Roundtree, adding that Bell stayed inside a relative’s house for most of the fighting and had just emerged to see what was happening. “The person who stabbed him was a friend of his. He wasn’t the intended victim.”

Bell fled in a car and stopped for help when he saw a uniformed office in a patrol car. By the time he got medical aid, the sheriff said, he had already lost a tremendous amount of blood.

Authorities have arrested nine people — men and women ranging in age from 18 to 39 — and charged each with aggravated assault and felony murder. Georgia law defines felony murder as a death caused during the commission of another felony. The charge does not require intent to kill and it carries an automatic life sentence.

The sheriff’s office identified Demetrius Lamont Harris Jr., 21, as the suspect accused of stabbing Bell.

The sheriff said all suspects charged in the case remained jailed today. It was not immediately known how many of them had defense attorneys.

Cheryl Karounos, spokeswoman for the Georgia Public Defender’s Office, said the agency’s Augusta office was representing one of the suspects, 35-year-old Quiauna Henley. She declined to comment further on the case.

Also charged were Quiasha Henley, 18; A’Lexis Cain, 18; Tyteanna Thomas, 18; Raheem Jobes, 19; Myah Dunbar, 18; and Terry Lee Daniels, 19.