Arizona boy has mini-meltdown upon learning he'll have a new sister in viral video

A six-year-old Arizona boy has achieved Internet fame after a video of him reacting to news he'll have a new little sister went viral.

The video shows Gunner Mertlich, along with his sisters Paisley and Harper, preparing to cut into a cake that will reveal the gender of their newest family member.

"I think it's a boy," Gunner tells his father Jason.

But the cheery tone of the video takes a dramatic turn as soon as Gunner slices the cake to reveal a bright pink center. The boy bursts into tears, crying, "I knew it was a girl!"

Jason asks Harper and Paisley if they're happy with the news, and both girls are pleased. When he asks Gunner, the answer is quite different.

"No, it's stupid," Gunner says in the video. "Every time it's girl, girl, girl, girl. It's always gonna be girls."

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In an interview with, Gunner seemed to have come to terms with the news, saying he was "happy" about his new little sister.

The video's popularity has stunned the Mertlich family.

"We wanted to tape it so all of the relatives could see what we're having," Jason said. "We knew he was going to be disappointed ... I didn't know he was going to go to that magnitude."

Mother Tiffany Mertlich said it took Gunner about an hour to calm down after learning he would have a little sister instead of a brother, but finally accepted his fate - and ate the cake.

"He finally came to, had some cake," Tiffany said. "He took it pretty well after that."