Who is Pete Davidson and why is everyone worried about him?

PHOTO: In this March 14, 2015, file photo, Pete Davidson speaks at a Comedy Central Roast in Culver City, Calif.PlayAP
WATCH Pete Davidson pens open letter to fans about mental health, online trolls

“Saturday Night Live” cast member Pete Davidson stunned and frightened friends and his social media followers with a disturbing post about his mental health on Saturday, which proved alarming enough to draw both his ex-fiancee, singer Ariana Grande, and New York police to NBC headquarters at 30 Rockefeller Center in Manhattan, which houses the late night comedy institution.

“i really don’t want to be on this earth anymore," Davidson posted on Instagram on Saturday afternoon. "i’m doing my best to stay here for you but I actually don’t know how much longer I can last,” the “SNL” comedian said on Instagram. "all I ever tried to do was help people. just remember I told you so.”

His account was shut down by Saturday evening, but not before Grande apparently showed up at 30 Rock in a panic.

"I'm downstairs and I'm not going anywhere if you need anyone or anything. I know u have everyone u need and that's not me, but i'm here too," Grande tweeted in a post that was later deleted.

A New York Police Department (NYPD) officer also made a visit to NBC headquarters in midtown Manhattan, according to an NYPD spokesperson, who confirmed to ABC News that the officer did what is known as a "wellness check" on the comedian at his workplace, and that they "made contact."

Davidson proved to be safe and sound and working on Saturday night’s live show. But the scare has drawn new attention to a young breakout star who has found himself in the spotlight this year like never before.

He did not appear in any sketches on the Dec. 16 episode, but he did introduce music guest Miley Cyrus' second performance of the night. He also appeared in a pre-taped sketch about the Oscars looking for a new host.

PHOTO: Pete Davidson poses in the press room at the 2017 MTV Video Music Awards at The Forum, Aug. 27, 2017, in Inglewood, Calif. Jason LaVeris/FilmMagic/Getty Images
Pete Davidson poses in the press room at the 2017 MTV Video Music Awards at The Forum, Aug. 27, 2017, in Inglewood, Calif.

The 6-foot-2 beanpole comic has long been open and unguarded about his personal struggles, often turning them into great, if at times awkward, comedy.

Since a childhood tragedy that he has said in interviews shattered his world and nearly broke him, Davidson has survived depression, addictions, sobriety and the dizzying ascent of his public profile this year when he became engaged to Grande, a pop powerhouse with a global following.

He has said that he has been plagued by mental health issues stretching back to his childhood, when, he has said, he pulled out so much of his hair that he was briefly bald.

For Davidson, “SNL”'s youngest-ever cast member, who joined the cast four years ago, 2018 has been a year full of challenges -- both personal and professional.

'The biggest crush in the whole world'

He began dating Grande in the spring and the couple were engaged by June. That month, Grande released her new album, "Sweetener," which included a song called "Pete."

That short-lived affair didn’t survive 2018, but it played out in spectacularly public fashion –- with Grande issuing adorable social media posts about him and Davidson making light of the unlikely partnership in appearances on “SNL.”

In August, Davidson said that he and Grande actually decided to marry the day they met.

For her part, last summer, Grande told Jimmy Fallon that “we weren’t even friends for a long time but I had the biggest crush in the whole world on him the whole time.”

They got tattoos memorializing their love and even bought a baby pig as a house pet.

By September, Davidson said that he had been threatened with violence over the relationship.

"I got a death threat,” he told Howard Stern in an interview. “Someone wanted to shoot me in the face because she’s so hot. Do you know how insane that is? I was like, 'Am I that ugly that people want to shoot me in the face?'"

By October, the couple had split up.

Then came November, when Davidson prompted a stinging public backlash after an “SNL” segment in which he playfully mocked an eye-patch worn by Texas Republican congressional candidate Dan Crenshaw, a former Navy Seal who sustained the injury during the war in Afghanistan.

Crenshaw made a surprise appearance on the following week’s "Weekend Update" segment with Davidson. Crenshaw took his turn playfully mocking Davidson, whom, when the laughs died down, shared both an apology and his own personal tragedy.

'The worst thing that could ever happen to anybody'

Davidson has long-acknowledged that the death of his firefighter father in the 9/11 attacks on the World Trade Center fundamentally changed him.

Pete was 7 when his father and five other New York firefighters (FDNY) charged across the Brooklyn Bridge towards the World Trade Center towers, and were last seen racing up the stairs to help evacuate guests from the Marriott World Trade Center Hotel -– which was destroyed when the towers collapsed.

PHOTO: Pete Davidson and Ariana Grande attend the 2018 MTV Video Music Awards on Aug. 20, 2018 in New York. Jeff Kravitz/FilmMagic/Getty Images, FILE
Pete Davidson and Ariana Grande attend the 2018 MTV Video Music Awards on Aug. 20, 2018 in New York.

Scott Davidson was a legendary cut-up among friends and colleagues, according to the New York Post.

“Scott was always clowning around,” Jaime Hatton Cregin, the elder Davidson’s former schoolmate at Staten Island’s St. Joseph by-the-Sea High School told the newspaper. “Telling jokes, making people laugh.”

Retired firefighter John Sorrentino said that Davidson had a “brutally honest” sense of humor.

“He had the ability to insult you but make you feel good about it.”

Davidson has his father’s FDNY badge number, 8418, tattooed on his left arm, according to the New York Times.

“There’s nothing I won’t joke about, and I think it’s because of what happened to me,” he told the newspaper in 2015 feature profile, seemingly in reference to his father’s death.

“That’s the worst thing that could ever happen to somebody. Now it’s just like, ‘Who cares, man?’”

PHOTO: In this March 14, 2015, file photo, Pete Davidson speaks at a Comedy Central Roast in Culver City, Calif. AP
In this March 14, 2015, file photo, Pete Davidson speaks at a Comedy Central Roast in Culver City, Calif.

But he said that suicidal thoughts haunted him during the years after the 9/11 attacks, pinning his survival to music.

"I would've killed myself if I didn't have Kid Cudi," Davidson said at the time. "I would've killed myself. Absolutely 100 percent. I truly believe if Man on the Moon didn't come out, I wouldn't be here," he said, referring to the artist's 2009 debut album, "Man on the Moon: The End of the Day."

Davidson first appeared on television at the age of 15 on an MTV comedy series and went on to be featured on Comedy Central’s popular "Gotham Comedy Live," a platform to feature up-and-coming comics. More reality and comedy series appearances followed.

He played a bit part in a Judd Apatow film and met SNL cast member Bill Hader, who later hustled him an audition with Lorne Michaels.

He was only 20 when he joined the "SNL" cast in 2014.