The 17-year-old Nashville school shooter who killed a teenage girl before turning the gun on himself allegedly left a dark trail of hateful online postings and appeared to be a “self-loathing incel,” according to the Anti-Defamation League.

Teen shooter Solomon Henderson expressed a wide array of troubling views in a purported manifesto and on social media before gunning down 16-year-old Josselin Corea Escalante at Antioch High School on Wednesday, ADL representative Carla Hill told The Post Wednesday night.

“What happens on the incel forums … is that people of color are told the only reason they’re incels is because of their color and so it pushes them toward other extreme ideology that he apparently took on,” Hill said.

“He picked up antisemitism, he posted a lot of anti-black content because of that … internalized racism,” said Hill, who is senior director of investigative research at the organization.

Metro Nashville police said Wednesday night investigators were probing “very concerning online writings and social media posts” as they attempt to determine a motive behind the attack that was partially streamed online.

Escalante was fatally shot inside the cafeteria of the school and another student was grazed in the arm.

Henderson then fatally shot himself before a confrontation with police.

Alleged online writings reviewed by outlets included Henderson stating that he “was ashamed to be black,” WTVF reported.

Other materials tied to Henderson obtained by the station included a layout of Antioch High School, photos of handguns and cartridges to load the weapon.

Henderson also posted antisemitic writings and posted a flyer from the Goyim Defense League, which is a neo-Nazi white supremacy group, WTVF reported.

“I was so miserable. I wanted to kill myself,” he also allegedly wrote at one point.

“I just couldn’t take anymore. I am a worthless subhuman, a living breathing disgrace. All my (in real life) friends outgrew me act like they didn’t f–king know me. Being me was so f–king humiliating. That’s why I spend all day dissociating.”

He also had a photo of the Covenant School shooter who killed three children and three staffers in 2023 before also killing herself.

Purported writings reported on by the Tennessean included statements against “race-mixing” with a desire to “take revenge” on society. Henderson also had statements praising Adolf Hitler and jarring photos from past school shootings, the newspaper reported.

The ADL Center on Extremism reviewed the purported manifesto and social media posts from the shooter, as well as a forum he allegedly participated in that promoted white supremacy and accelerationism, which is the desire to see a hastening to the collapse of modern society, according to the civil rights organization.

“He’s in an incel forum that’s telling him he’s an incel because he’s black, no one wants you because you’re black,” Hill, of the ADL, said of one online space.

Henderson was also part of a gore forum where mass killers of all ideologies are often celebrated, including the recent Madison, Wisconsin shooter, according to the ADL.

The shooter partially livestreamed the shooting on the online platform Kick, according to the company.

“We extend our thoughts to everyone impacted by this event,” Kick wrote on X.

“Violence has no place on Kick. We are actively working with law enforcement and taking all appropriate steps to support their investigation.”