Elon Musk fired most of Twitter's staff and said their talents will be of 'great use elsewhere.' Twitter's now threatening to sue Meta, accusing the company of hiring former employees to create a 'copycat' app.

• Meta launched a text-based app called Threads that competes with platforms like Twitter.
• In less than 24 hours, Elon Musk's lawyer sent a cease-and-desist letter over Meta's app.

About eight months before Meta launched its text-based app, Threads, Elon Musk purchased Twitter and swiftly went on a firing spree, laying off almost half of the company's 7,800 employees at the time.

The decision was met with some criticism, but Musk appeared to show little remorse — in one tweet writing that he would like to "apologize for firing these geniuses."

"Their immense talent will no doubt be of great use elsewhere," he continued.

Now, Musk's attorney is going after Meta, alleging that the company hired some of those laid-off employees to make a rival social media app.

Less than 24 hours since Meta launched Threads, Musk's attorney Alex Spiro sent a cease-and-desist letter to Meta CEO Mark Zuckerberg, accusing the company of hiring "dozens of former Twitter employees" to create a "copycat" app.

Some of those employees "continue to have access to Twitter's trade secrets and other highly confidential information" and "improperly retained Twitter documents and electronic devices," the letter claims.

"Based on recent reports regarding your recently launched 'Threads' app, Twitter has serious concerns that Meta Platforms ('Meta') has engaged in systematic, willful, and unlawful misappropriation of Twitter's trade secrets and other intellectual property," it said.

A source familiar with both companies previously told Insider that there are a handful of ex-Twitter employees at Meta, but none of them are currently working on Threads.

Meta's communications director Andy Stone wrote in a Threads post that "no one on the Threads engineering team is a former Twitter employee — that's just not a thing."

Spiro did not respond to a request for comment.

Since the Tesla founder took over Twitter, Musk said in a BBC interview that he had laid off about 80%, or 6,500 Twitter employees, whittling the company down to fewer than 600 engineers.

Musk said firing that many employees was "one of the hardest" decisions and that it was "not fun at all. Painful."

Twitter has also since introduced a slew of controversial changes under Musk, including fewer content moderation rules and a verification process that costs $8 a month.

Meta employees have seen the chaos at Twitter as an opportunity to create a rival app for months, The New York Times previously reported.

Threads officially launched on Wednesday and garnered about 30 million sign-ups by the next morning, according to Zuckerberg.