A mother's letter in support of her son's coming out on Facebook has gone viral.

After seventeen-year-old Zach Gibson came out gay on Facebook, his mother, Michelle McClain, responded with a letter of support.

“I was surprised by your Facebook post where you came out,” the St. Louis mom wrote. “I want you to know that I love you unconditionally. I love you with my actions, not just words. I'm so proud of you. You are the bravest person I know. I'll fight for you always. Your sexual orientation does not define you. You are still the boy who forever won my heart.”

She added: “The only thing that concerns me is the number of empty soda cups and tea bottles in your room. Throw them away before ants come inside.”

Nearly 6 million people have read the letter on social media.

Appearing on cabler HLN, McClain said that she was encouraged by her brother to post the letter on the Facebook page of Have a Gay Day.

“I'm not really surprised by her letter, because it's typical of my mom to say what she said,” Gibson said. (The video is embedded on this page. Visit our video library for more videos.)