Police arrested Martin after a threatening post on social media. 12up shared a photo from Martin's Instagram story showing a shotgun and shotgun shells while listing his former high school, Harvard-Westlake High School in Los Angeles:
According to TMZ Sports, authorities placed Martin on a 72-hour hold shortly after his arrest in the belief "he was a possible danger to himself and others."
The Instagram post came a little more than a week after a mass shooting Feb. 14 at Marjory Stoneman Douglas High School in Parkland, Florida, that killed 17 people. Harvard-Westlake closed school the same day the post surfaced on Martin's account.
TMZ Sports reported Martin began sending "disturbing messages" to two of his former classmates at Harvard-Westlake beginning in 2016.
"And I blame you above all," Martin allegedly said in one message. "You'll get yours, eventually—I have already paid my price for being a bad person. I wish you nothing but the worst. Best, Jonathan Martin."
In the photograph of the shotgun, Martin tagged Richie Incognito and Mike Pouncey, two players who were central in the Miami Dolphins' bullying scandal.
NFL investigator Ted Wells wrote in his 2014 report that Incognito, Pouncey and teammate John Jerry "engaged in a pattern of harassment directed at not only Martin, but also another young Dolphins offensive lineman... and a member of the training staff."