A Tesla board member once locked Elon Musk's phone in a safe to keep him off Twitter. The billionaire forced hotel security to open it, biographer says.

• Antonio Gracias once locked Elon Musk's phone in a hotel safe, biographer Walter Isaacson said.
• The move by the Tesla board member was meant to stop Musk from tweeting late into the night.
• It didn't work. Musk got hotel security to unlock the safe around 3 a.m., Isaacson said.

Even Elon Musk's friends aren't too happy with his tweets.

Some of Musk's friends have taken drastic measures to try to keep him from tweeting late into the night, according to Musk's biographer, who has been shadowing the billionaire for the better part of three years.

Tesla board member and close Musk confidant Antonio Gracias once took Musk's phone away to prevent him from tweeting late into the night, Isaacson said during a Twitter Spaces event on Wednesday.

"At one point when Elon was firing off tweets without filtering them in the least, they were on a trip and Antonio took his iPhone — Elon's iPhone — and locked it in the hotel safe with Antonio punching in the code so that Elon couldn't get up at 3 a.m. and start tweeting again," Isaacson said, describing Gracias as "one of Elon's closest friends."

Musk later got hotel security to open the safe at around 3 a.m. so he could start tweeting again, Isaacson said.

The biographer added that Musk is "almost addicted to the drama that comes with Twitter" and sees owning Twitter as a way he can be "king of the playground."

"It's something he loves — loves almost to the point of compulsion," Isaacson said, adding that some of his friends, including his brother Kimbal Musk, attempted to convince him not to buy Twitter.

Gracias and Musk did not respond to Insider's requests for comment ahead of publication.

It's unclear when Gracias attempted to lock Musk's phone away. Though, the Tesla CEO has faced his fair share of controversy regarding his tweets over the years. In 2018, Tesla investor Ron Baron advised Musk to stop tweeting when he's annoyed or angry.

"If something really upsets you, go for a walk around the factory. Get an ice cream cone. Just don't use Twitter," Baron told Musk.

Baron sent the email after the CEO called a British cave diver who helped rescue a group of boys that were trapped in a cave a "pedo" on Twitter. Musk later apologized for the tweet about three days after Baron's email and the "pedo" comment eventually spawned a defamation lawsuit which Musk won in 2019.

The email exchange was uncovered during a trial over Musk's "funding secured" tweet, which the billionaire also won. Though, Musk and Tesla each paid the Securities and Exchange Commission a $20 million penalty in 2018 over the tweet in which Musk said he would take Tesla private.

Twitter's new CEO also once told Musk he shouldn't tweet late into the night and the billionaire has admitted he should probably stop tweeting at 3 a.m.

"Have I shot myself in the foot multiple times? Yes," Musk said during a BBC interview earlier this year. "I think I should not tweet after 3:00 a.m. If you're gonna tweet something that maybe is controversial, save it as a draft then look at it the next day, and see if you still want to tweet it."

Musk has long been known for his juvenile sense of humor and unfiltered, combative nature. On Twitter, his tweets have ranged from low-brow sexual humor and jokes about marijuana, to theories on life on Mars and initiating feuds with the likes of Apple's CEO Tim Cook and Amazon founder Jeff Bezos.