STUDIO CITY—Last month, former NFL Miami Dolphins offensive lineman Jonathan Martin was arrested for a suspicious Instagram post where he made threats to shoot up the  Harvard Westlake campus. Martin has pleaded not guilty to the criminal threat charges brought against him.

The picture, posted on February 23, depicts the athlete with a semi-automatic shotgun and shotgun shells on a bed. Tagged in the photo were the accounts of two Dolphins players and two classmates, as well as a message that read “When you’re a bully victim & a coward, your options are suicide, or revenge.” He put two hashtags on the gun: #HarvardWestlake and #MiamiDolphins.

The post led to a shutdown of the Harvard-Westlake campus located in Studio City. Two of the accounts tagged were from former classmates that allegedly bullied him while he attended the high school. School officials sent an e-mail to the student body shortly after learning of the Instagam post.

“The safety of our students, faculty, and staff is always our primary concern. So, out of an abundance of caution, we made the decision to close school today,” the message read.  “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.”

According to reports, Martin graduated from the school in 2008. In 2013, the athlete kicked off a bullying scandal that lead to investigations by the Miami Dolphins organization and the NFL where he alleged he was the target of bullying from teammates, some which was reported to be racial in nature.

One of the men tagged in the post, NFL player Richie Incognito, was suspended for the entire 2014 season as a result of the investigations. The other teammate mentioned, Mike Pouncy, was also implicated. Martin retired from the league in 2015.

Martin faces four felony counts of criminal threats and a misdemeanor count of possessing a loaded firearm. If convicted, he could spend up to six years in prison. He will reappear in court on April 25 in Van Nuys to determine a date for his hearing.