CHICAGO — Gus Walz sat in the front row for the biggest moment of his father’s life, and his pride exploded out of him.

“That’s my dad!” the 17-year-old yelled. He stood, tears streaming down his face, and pointed to his father, Tim Walz, the governor of Minnesota, who was accepting the Democratic nomination for vice president in a speech to thousands of people in a packed arena and millions more watching at home.

The teen’s exuberance captured hearts and went viral, becoming perhaps the defining image of his father’s address and further humanizing a running mate picked by Vice President Kamala Harris in no small part for his everyman appeal.

Gus wept through much of his father’s speech, and when it was over, climbed on stage with his family and wrapped his dad in a tight bear hug, burying his face in his shoulder.

The viral moment inspired reactions from all over social media, including from U.S. Sen. Amy Klobuchar.

“You know you’ve done well as a parent when your kids are as proud of you as Gus and Hope are of Tim Walz. ‘That’s my dad.’ No three words better describe our next Vice President,” Klobuchar said on X.

Gus is a high school senior. His parents recently disclosed to People magazine he has a non-verbal learning disorder, ADHD and an anxiety disorder. They called his condition “his secret power” and said he’s “brilliant” and poised for success.

Unlike learning disorders that make it difficult for a child to learn to read, a non-verbal learning disorder affects different kinds of learning, including the ability to notice patterns and learn concepts, according to the Child Mind Institute.

“These include visual patterns, social patterns, and concepts in language and math,” the organization notes on its website.

Those with a non-verbal learning disorder may also have trouble with non-verbal social cues such as body language and facial expressions.

When Tim Walz was elected governor, Gus Walz cheered because it meant he could get a dog. They adopted a black lab named Scout a few months later. Gus Walz got his driver’s license last fall. 

Gus Walz is getting his own turn in the spotlight after his older sister, 23-year-old Hope Walz, delighted Americans with the playful social media videos she filmed with their dad.

Tim Walz talks often about the fertility treatments his wife, Gwen, underwent to get pregnant with Hope, a journey he says inspired her name. He’s also said that Gus was born because of reproductive health care like IVF. 

As he told the story Wednesday, Hope made a heart with her hands and held it over her chest.

“Hope, Gus and Gwen,” Walz said to his family, “you are my entire world, and I love you.”

Now in his second term as governor, Tim Walz, 60, also served 12 years as a U.S. congressman before his successful 2018 run to lead the state.

Harris announced Tim Walz as her running mate earlier this month. 

“As a governor, a coach, a teacher, and a veteran, he’s delivered for working families like his,” Harris said in the announcement. “It’s great to have him on the team.”

Walz was among a deep bench of potential running mates that included Sen. Mark Kelly of Arizona, Pennsylvania Gov. Josh Shapiro and Kentucky Gov. Andy Beshear. 

contributed to this report.