Miami Dolphins ex-lineman Jonathan Martin has reportedly been detained while police investigate an incident surrounding a disturbing picture he shared on Instagram, law enforcement told TMZ.

The firearms-focused post came at a time when the nation's sensitivities about guns have been heightened by mass shootings and violence. After the devastating shooting deaths of 17 people at a high school in Parkland, Fla., people around the country are engaged in a heated debate over guns.

Sgt. Barry Montgomery of the Los Angeles Police Department told Fox News that "the individual we believe to be responsible for the social media post has been detained and the investigation is ongoing." He would not, however, confirm the identity of the person being held.

Martin allegedly posted a picture to his Instagram that showed a shotgun surrounded by shells with the caption “when you’re a bully victim & a coward, you options are suicide, or revenge.”

In the post he tagged two former teammates, Richie Incognito and Mike Pouncey, with whom he had been bullied by in 2013, as well as his former high school Harvard-Westlake in Los Angeles.

Officials at Harvard-Westlake were forced to close the school’s campuses and sent an email out informing students of the incident,The Los Angeles Times reported.

"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 email read. "The school's private security team is working with the Los Angeles Police Department, which is present on both campuses.”

The email added that there was no “imminent threat” to the students.

Martin entered the spotlight in 2013 when he accused Incognito and Pouncey of harassment in the locker room. An NFL investigation found that Martin was indeed being harassed.

He retired in 2015.

Martin’s disturbing post comes just a week after a lone gunman opened fire in a Florida high school, killing 17 students.

Film at 11... 🤔

To me this is an anti-bulling statement not a threat... I could be wrong but that's how I read it... 😟

It’s a challenge.

An accused bully is sending the message to those that accused him:

“when you’re a bully victim & a coward, you options are suicide, or revenge.”

you are a coward. do something about it (bring it on) or kill yourself.... sounds like the accused bully may well be one. It's not hard to comprehend. I'm not saying there wasn't an overreaction but comprehension is important LOL

I hate that word though and think its over used.

Uh........

He was the one bullied...

so it looks like he is saying his only options are revenge or killing himself right? still a threat?

NFL has gotten soft by historical standards.

This dude is nuts, keep him off the zoloft.

Damn foose ball players!!!

Now that's deep!

Impressive.

.. with some fava beans and a nice chianti