It was Labor Day weekend, and Chelsey Ryan, 22, was hosting a birthday party for her mom in her Harford County, Md., back yard. Ryan and her friends were waiting for their turn to play beer pong. As she waited, Ryan chatted on the phone with a relative who couldn’t attend the party himself.

“I was talking on the phone to my cousin,” Ryan told The Washington Post by phone Wednesday. “He’s in the Navy, stationed in Hawaii. We don’t get to talk much because of the time difference.”

She told him that Jonathan, their 5-year-old cousin, was being particularly energetic that day. They’re both godparents to the child; she wanted him to see Jonathan in action for himself. “I Snapchatted him a video,” she said.

This is the video she happened to record. Please watch it several times, with sound.

Knife Kid — a four-second video of a kid with a knife — has since gone viral. It had more than 80,000 retweets by Wednesday morning, after Ryan’s friend Madison Meyers tweeted it out over the weekend, a couple of weeks after it was initially filmed. The short clip is a masterpiece of virality: It involves a kid, an element of danger and perfect comedic timing (“A knife!” “NO!”).

Ryan spoke to us by phone about Knife Kid after getting permission from Jonathan’s parents to talk about it.

And first things first: The “Knife Mom,” as the woman who bellowed “NO!” has since become known, is not actually Jonathan’s mom. “Knife Mom” is April Holsapple, 21, a friend of Ryan’s and of no relation to the family, who was waiting over by the beer pong table while Ryan recorded the video. Jonathan’s real parents were both out of frame with a larger group of barbecue-goers.

Jonathan, Ryan said, “has the best personality. He’s so funny. He makes anybody around him laugh.” But he’s also kind of a troublemaker.

“I saw Jonathan running around the pool,” Holsapple said via a Twitter DM. “I’ve always had a big mom instinct with people. … So I asked what he had. When he screamed he had a knife I just panicked and went worst case scenario that he was gonna hurt himself or do something bad.”

The 5-year-old really was running around the yard with an actual knife, Ryan said. It was a closed pocket knife. How’d he get it? “He went into my uncle’s pocket and pick-pocketed it out of there,” Ryan said.

Seconds after the video ended, pretty much every adult at the party raced to catch Jonathan, whom Ryan described as a very fast runner. Jonathan and A knife! were grabbed by Grace, Ryan’s sister, who was waiting on the other side of the pool to cut off the kid. Nobody was hurt.

Jonathan’s parents have reminded him that things like stealing a knife and running around with it are wrong and dangerous, although Ryan said Jonathan definitely knew he was doing something he shouldn’t as he ran around the pool with A knife!

“He knew it was wrong,” she said. “We talked to him again the other night when I was Facetiming him. We said, ‘Jonathan, you know this is not okay.’ But he just laughed.”

As it turns out, “A knife!” almost wasn’t a viral video; just as it was filmed by chance, it was shared by chance as well.

Meyers, 16, tweeted the video very early Sunday morning, while she, Holsapple and Ryan were on their way back from a Sam Hunt concert in Virginia. Meyers was bored and trying to stay awake, so she decided to look through Ryan’s Snapchat memories. Re-watching “A knife!,” she decided to tweet it.

“We … all laughed so much, I thought it should be shared,” Meyers said over a Twitter DM.

Ryan and Meyers didn’t really think many people would see the video, which was tweeted out at 2 a.m. from an account with a few hundred followers. But when Ryan woke up Sunday to watch the Baltimore Ravens game, she saw the tweet had a few hundred shares. The next day, a few thousand. And on Wednesday morning, the video made it to the “Today” show.

Now that it has taken off, family and friends involved in its sudden fame are doing their best to enjoy it. They’ve been joking about tweets calling Holsapple the “Knife Mom” in a group chat. “My friends want me to change my Twitter name to ‘knife mom,’ and I intend on making it my Halloween costume now,” she said.

“A lot of tweets we’ve been getting back have been positive. You’re always gonna have a handful of haters,” Ryan said. Holsapple said she’d seen many tweets, mistaking her for Jonathan’s mother, accusing her of being a bad parent for playing beer pong at the party.

“We’ve been replying back and making sure they know everything was fine, and it was just a spur of the moment,” Ryan said.

Meanwhile, Meyers said that all the unexpected attention is stretching her phone to its limit. “My notifications have actually been freezing my phone every time I go onto Twitter,” she said. “I had to turn them off for a little bit.”

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