A 12-year-old Colorado student left heartbroken after going home with an unsigned yearbook is getting an overwhelming number of encouraging notes from people around the world. 

People from all walks of life have written letters to Brody Ridder, who just finished the sixth grade, reassuring him that he isn't the only one who has struggled with bullying, Brody Ridder's mom, Cassandra Ridder, told Fox News. 

Over the past several weeks, hundreds of letters written in various languages have been filing the Ridders' mailbox in Westminster. People are not only offering advice and words of encouragement. They are sharing their own personal experiences with bullying

"It's all age ranges, too," Cassandra Ridder said. "I just opened a letter from a 3-year-old that was telling his mom what to write."

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Cassandra said her son struggled to make friends this past year while attending The Academy of Charter Schools in Westminster. The school consists of students from kindergarten through 12th grade. 

"He was just bullied, teased … you name it, it's happened to him," Cassandra said. "He's tried to put himself out there to make friends … he'll get kids' phone numbers, and he will try to text them, but they will never respond to him. Or they're like, 'I don't want to talk to you'."

Cassandra can't understand why. 

"I don't know if the kids are just struggling socially from returning to in-person learning," she said. "I don't know what's going on." 

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At the end of May, the students were given their yearbooks. While many students went home with signatures and kind notes, Brody's yearbook remained nearly empty. 

When Brody got home, he started to tear up, his mom recalled. His classmates told him they were too busy and that he wasn't important, she said. 

When she looked through the book, she recalled seeing two names. There were no notes beside them, either, she said. But that's not all. 

Brody Ridder and classmates

Cassandra Ridder's son Brody and students at his school in Westminster, Colorado. (Cassandra Ridder )

"I saw that Brody had signed it himself. And he said, ‘I hope you make some friends’," she said. "It really broke my heart." 

Shortly after, Cassandra posted about the incident in a Facebook group filled with other parents at the school. She also reminded the parents to teach their kids how to be kind. 

What she didn't expect was for several parents to message her back. They asked her what class Brody was in, so their kids could stop by and say hello on the last day of school. 

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Before Brody left for the last day of school, Cassandra reminded him that "Ridders aren't quitters" and handed him his yearbook. 

On May 24, during the school's end-of-year celebration, dozens of students from other grades lined up to sign Brody's yearbook and send him off with warm messages for the summer. 

Brody Ridder's yearbook signatures

Brody Ridder's yearbook full of signatures.  (Cassandra Ridder )

Once the older kids started to line up, so did the kids in his class. 

"It was like a domino effect," Cassandra said. "It was beautiful." 

There were more than 100 signatures and "everybody had nothing but nice things to say," she recalled.

However, Brody's story doesn't end there. Paul Rudd, who plays the title character in Marvel's "Ant-Man" films, also contacted Brody. 

Brody Ridder gift from paul rudd

Paul Rudd sent 12-year-old Brody Ridder a gift after his yearbook went unsigned.  (Cassandra Ridder )

Suddenly, Cassandra was getting messages from people all over the world who related to her son's story. 

They had asked if it was possible to sign a virtual yearbook for him, but Cassandra had a better idea. She posted their P.O. Box on Facebook so that anyone could write him. 

To date, they have already gotten at least 600 letters, and they are still coming. 

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"I cry with the majority of them I read because these people are just … they relate," she said. "They've been through it, too." 

Cassandra plans to make a book out of all the letters one day so whenever Brody is having a tough day, he can pull out it out for some encouragement. 

When in doubt, he also has Ant-Man's personal phone number too.