Charli D'Amelio and Landon Barker have stepped out hand in hand.

On Tuesday night, the TikTok star and the punk-rocker, both 18, were spotted holding hands leaving the afterparty that followed Machine Gun Kelly's sold-out show on at Madison Square Garden in New York City. Landon made a surprise appearance on stage during the Mainstream Sellout Tour stop, walking out to perform his "Die in California" collab with MGK from the 32-year-old singer's Mainstream Sellout album.

The teen performed after TMZ published photos of his dad Travis Barker being wheeled into Cedars-Sinai Medical Center in Los Angeles on a stretcher earlier in the evening, with wife Kourtney Kardashian by his side.

PEOPLE editor Nigel Smith, who attended the concert, said Landon seemed "very emotional" after coming out on stage for a second song inspired by the recent death of his friend Cooper Noriega, a TikTok star who died at 19 on June 9. At one point, Landon shared an embrace with MGK, a family friend who attended Travis and Kardashian's May wedding in Italy.

"Landon came out during the song and seemed to be working out some demons," he said. "They hugged onstage during the performance, singing and shared an emotional moment at the end of the song before Landon walked off."

RELATED: Travis Barker Hospitalized in Los Angeles, Wife Kourtney Kardashian by His Side: Report

Machine Gun Kelly/Instagram Landon Barker

Though it is unclear why the Blink-182 drummer, 46, was taken to the hospital, fans noted a tweet he released earlier Tuesday, which read, "God save me." However, many social media users pointed out that the message shares the name of a song by MGK.

Travis' 16-year-old daughter, Alabama, asked her followers to "please send your prayers" in an Instagram Story shortly after her dad was reportedly taken to the hospital.

A rep for the rocker had no comment. PEOPLE has also reached out to Karadshian's rep for comment.

Phillip Faraone/Getty Travis Barker and Landon Barker

Landon's surprise Manhattan performance – and display of PDA with D'Amelio – comes one day after a source told PEOPLE that the teens were spending time together.

"They're seeing each other, and it's early stages," the source said.

Romance speculation heated up after the new couple was photographed leaving Landon's concert together earlier this month.

RELATED: Charli D'Amelio and Landon Barker Are Dating: 'It's Early Stages,' Says Source

The rumors were further fueled when the two both shared Instagram Stories of new tattoos they received from the same Los Angeles-based artist (@ar.bel) earlier this week.

The stars were also reportedly spotted leaving the party for D'Amelio's sister Dixie's debut album a letter to me in Los Angeles together.

D'Amelio was previously linked to musician and fellow TikTok star Chase Hudson (a.k.a. musician Lil Huddy). After they were first confirmed to be a couple in December 2019, she announced their split via her Instagram Story in April 2020.

"Since you guys have watched mine and Chase's relationship from the start, I decided I needed to tell you all that we are no longer together," she wrote at the time. "It hurts me to say this, but we've decided that this is what's best for both of us."

Amy Sussman/Getty; Kevin Mazur/Getty Charli D'Amelio and Landon Barker

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D'Amelio added, "We are still close friends and I would not change that for anything! I truly have so much love for Chase and wish him nothing but the best for him. It makes me happy to see all of the great things he has going for him."

Landon is rumored to have dated social media star Devenity Perkins in 2016, but he's not been linked to anyone in recent years

He recently spoke to PEOPLE about having his song "Die in California" featured in Mainstream Sellout.

"It's an amazing feeling," he said in May. "I feel great every single time the song comes on. It was originally just like a song I was working on and Kels (MGK) came into the studio and he loved it and we ended up working it out and putting on the album. So, it's honestly something I'm very proud of."

On Late Night With Seth Meyers Wednesday, Machine Gun Kelly spoke about his self-sustained, and very bloody, head injury while performing at Madison Square Garden in New York City one night earlier. The avoidable accident occurred when Kelly broke a champagne flute over his head, causing a significant cut near his right eye. “You know when you clink a champagne glass with a fork? Yeah, I didn’t have a fork,” Kelly said. “So I just clinked it on my head.” Following the incident, Kelly had blood running down his chest and on his hands. He even almost reopened the wound while on Late Night because he was wearing several rings and rubbed his face. As Meyers pointed out, given the nature of the injury, Kelly kind of had it coming. “You know what?” Meyers asked. “In medicine they call that asking for it.” “Yeah,” Kelly replied, “so I had a serious case of that last night.”

"I was deeply unhappy, barely containing secrets that would soon devastate me emotionally and send me to the brink of suicide at the height of my fame."

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