"It made me feel a little lost in the world."

Former A's catcher Bruce Maxwell made history on Sept. 23, 2017, by being the first MLB player to kneel during the national anthem in protest of racial inequality and police brutality.

He detailed that day to NBC Sports Bay Area/California in NBC Sports' documentary, "HEADSTRONG: Mental Health and Sports."

"When I got to the field, I immediately walked into my manager's office -- had a sit down with him and our GM in private, told them what I was going to do, told them how I was going to go about it -- told them my plan, reasons, and shed a few tears because it's a heartfelt subject for me ... "

Maxwell knew the backlash he would receive, he just wasn't prepared for the magnitude of it. He received death threats -- and still does to this day.

"The fact that somebody actually took the time to find out what school my sister coached basketball at in Texas, somebody took the time to find out where my mother lived," he explained.

Maxwell then admitted he rarely left home when he headed back to Arizona following the event.

"I was miserable," he said.

He didn't want to do anything. Not exercise, not even talking to his parents.

"At that moment in time, I was standing for something way bigger than myself," Maxwell explained.

Just a few weeks later, the 28-year-old made headlines once again when he was arrested at his home in Scottsdale, Ariz. and charged with aggravated assault with a deadly weapon and disorderly conduct after he allegedly pointed a gun at a food delivery worker.

Maxwell told NBC Sports Bay Area/California he was in a certain mental state, and in addition to what was currently going on, he felt he needed to grab his gun in order to protect himself.

"I'm in my house, I'm defending myself, just in case this happens to be one of these crazy-ass people that are sending me threats," Maxwell said

He didn't feel like himself. Not even like a human being, he explained.

[RELATED: Marcus Semien shares mental health journey]

But now, he's freely talking about it and wants to leave his mark on the world with more than just what's going on between the foul lines.

You can watch all of the "HEADSTRONG: Mental Health and Sports" vignettes right here. The full documentary will play all month on NBC Sports Bay Area and NBC Sports California.

Check our channel listings page for times and dates.