STUDIO CITY (CBSLA/CBS Sports) – Former NFL player Jonathan Martin is facing multiple charges in connection with a threat last month posted to social media that forced the closure of his former Studio City high school, according to multiple reports.

The Los Angeles County district attorney’s office last week charged Martin with four felony counts of making criminal threats and one misdemeanor count of carrying a loaded firearm in public, according to the Los Angeles Times.

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A warrant has been issued for his arrest. He was expected to turn himself in to authorities Tuesday, the Times reports.

On Feb. 23, Harvard-Westlake closed both its high school campus in Studio City and its middle school in Holmby Hills after a post on Martin’s Instagram account showed a shotgun and referred to his former prep school by name.

The post had the text: “When you’re a bully victim & a coward, your options are suicide, or revenge.”

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The image included “#HarvardWestlake” and “#MiamiDolphins” superimposed over the shotgun, along with social media handles for former Miami Dolphins teammates Richie Incognito and Mike Pouncey, and a pair of former Harvard-Westlake classmates.

When Martin was detained that same day, TMZ reports, Los Angeles police found an ax, a knife and a loaded shotgun in his possession.

Martin was placed in a 72-hour psychiatric hold after he was detained, but was later released. According to court documents, Martin’s girlfriend said that had been making suicidal statements in the month leading up to his Instagram post. Martin had also been sending disturbing messages to two of his former high school classmates — James Dunleavy and T.J. Taylor — who were both named in Martin’s Instagram photo.

In 2013, while playing for the Dolphins, Martin was the victim in a bullying scandal that sparked a national conversation about the issue and resulted in Incognito’s suspension.

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Incognito currently plays for the Buffalo Bills. Martin retired from the NFL in 2015.