SYRACUSE, N.Y. – One of four teens arrested this week during a large fight at a Syracuse high school was previously convicted of killing an innocent man just three years ago.

Ander Grady, 18, currently faces a disorderly conduct charge for his alleged involvement in a brawl at Corcoran High School that ended with Grady threatening to knock an administrator “right the f*** out,” Syracuse.com reports.

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Police said the fight broke out when hundreds of students were in the hallway changing classes Monday afternoon. School security officers first attempted to break up multiple fights in the school’s common area before they called for reinforcements from Syracuse Police as the situation spiraled out of control, according to CNYCentral.com.

“The officers began to physically separate the suspect combatants but with each separation several other groups would begin to fight,” Syracuse Police Lt. Geno Turo told Syracuse.com.

Grady, as well as students Eric Floyd, 17, Isiah Norvel, 16, and Zavier Moreman, 17, were arrested for disorderly conduct, and Floyd faces an additional charge of resisting arrest.

Police allege Floyd attempted to fight officers as they subdued and cuffed him. School officials reportedly told Grady to leave, and he allegedly shouted “I’ll knock you right the f**** out, Murphy” to a school administrator, presumably vice principal Kevin Murphy.

The threat was apparently quite credible, as Onondaga County District Attorney William Fitzpatrick confirmed Wednesday that Grady was one of two young teens convicted in family court of killing 51-year-old Michael Daniels in 2013, according to the news site.

Grady, then 15, and a 13-year-old friend were reportedly playing the “knockout” game when they targeted Daniels, who was standing along outside of a local market when the boys kicked and pummeled him to death.

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Grady was sentenced as a 16-year-old to 18 months for second-degree manslaughter, the maximum allowed by law. It’s unclear exactly how much time Grady served behind bars.

Grady stayed the night in jail for his arrest Monday, and was back home by 10:44 a.m. Tuesday, according to his Facebook timeline.

The day before the fight, Grady posted: “So much going on I just am so tired of everything and I can’t take it no more. I’m ready to just say f*** everything.”

Many of his Facebook posts involve reposted videos of fights between black teens, drug use, scantily clad women, and various firearms, though some alluded to his recent troubles with the law. Grady’s Facebook profile picture shows several teens in a drugstore throwing gang signs, flipping off the camera, and posing with their fingers in a gun shape.

Several folks who posted about the school fight online were outraged that Grady was in the school to begin with.

“18 months of confinement for murder? And right back into our public schools?” Kala82 posted. “I can’t even type fast enough to keep up with the thoughts that are racing through my mind!”

“I was still reeling with anger last night that he was placed immediately back in to mainstream school. Who is responsible for placing all of the other students and the faculty in serious danger? Why was he not attending an alternative program where the teachers were given the option to teach him? I truly want to know the rationale behind that one,” MarisMami wrote.

“The teen served his eighteen months for beating an innocent man to death,” commenter TSMCT8 wrote. “Our elected officers feel this 18 year old can be rehabilitated and they want to give him several more chances to turn his life around.

“I’m just relieved Mr. Murphy was not harmed and he was able to make home to his family. How stressful.”

“Someone needs to clue this clown in on the fact that the ‘tough guy’ thing is not going to work out well for him!” Robert added.

“This is the reason my son will stay in a private school till the day I run out of money,” joescomputer posted. “This stuff will not stop and it is only going to get worse unless we move these people out of society for good. I don’t believe this is getting the publicity it deserves. This one really strikes a nerve with me.”