Dolphins tackle Jonathan Martin (71) watches from the sidelines during...

Dolphins tackle Jonathan Martin (71) watches from the sidelines during the second half of a game against the Jaguars in 2012. Credit: AP / Wilfredo Lee

Former NFL player Jonathan Martin was detained by Los Angeles police on Friday after an Instagram post showing a shotgun led to the closing of a Los Angeles-area high school.

The Los Angeles Police Department said Friday afternoon, “The individual we believe responsible for the social media post in question has been detained and our investigation is ongoing.”

The photo allegedly posted by Martin on Thursday shows a gun surrouned by ammunition on a white sheet and included the message: “When you’re a bully victim & a coward, your options are suicide, or revenge.”

The Instagram post also included hashtags for Harvard-Westlake, the private suburban Los Angeles high school Martin attended, and the Dolphins.

The Instagram post attributed to Martin tagged the accounts of former Dolphins teammates Richie Incognito and Mike Pouncey — whom he accused of extensive bullying in 2013.

Incognito was suspended indefinitely without pay by the Dolphins in November 2013 in response to the complaint. The NFL hired attorney Ted Wells to conduct an independent investigation into Martin’s accusations of bullying. Wells’ 144-page report released in February 2014 revealed that Martin and others were subjected to “a pattern of harassment” by Incognito and two other Dolphins players, identified as fellow offensive linemen John Jerry and Pouncey. The Dolphins traded Martin to the 49ers in March 2014.

Harvard-Westlake issued a statement on Friday announcing the closure of classes on two campuses.

“The safety of our students, faculty and staff is always our primary concern,” the school said in an email to staff and students, according to the Los Angeles Times. “We made the decision to close school today. The school’s private security team is working with the Los Angeles Police Department, which is present on both campuses. With these precautions in place, we believe there is no imminent threat to our campuses or our school community.”

Martin’s alleged post comes after 17 people were killed by a lone gunman at Marjory Stoneman Douglas High School in Parkland, Florida, on Feb. 14.

Martin retired in 2015 after he was released by the Panthers before the season.

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