SpaceX fired 5 employees after it found they had drafted and circulated a letter criticizing founder Elon Musk and urging executives to make the firm’s culture more inclusive.

On Thursday, The New York Times revealed that SpaceX has fired employees associated with the letter. The number of fired employees was not specifically stated.

According to The New York Times, SpaceX President Gwynne Shotwell said in an email that the company had looked into the letter and “terminated a number of employees involved.”

The employees who circulated the letter, according to Shotwell‘s email, were fired for making other employees feel “uncomfortable, intimidated and harassed, and/or angry since the letter pressured them to sign onto something that did not reflect their views,” according to the publication.

In a list of three demands, it said “SpaceX must swiftly and explicitly separate itself from Elon’s personal brand,” “hold all leadership equally accountable to making SpaceX a great place to work for everyone” and “define and uniformly respond to all forms of unacceptable behavior.”

In recent months, Musk, who is also the CEO of the electric car maker Tesla, has made headlines and did appear in late-night comedy monologues due to a variety of subjects, including his attempt to take over Twitter, his criticism of Democrats, and a rumored sexual harassment claim, which Musk has denied in a tweet.

The open letter at SpaceX was created recently and sent as an attachment in an internal “Morale Boosters” group chat that includes thousands of employees, as first reported by The Verge.

Musk, who serves as both the company’s CEO and chief engineer, has been credited with playing a key role in many of SpaceX’s notable achievements, including developing a method for the reuse of orbital rocket boosters and resuming regular human spaceflight from American soil after a nine-year break.

Shotwell, who oversees a large portion of the business’s daily operations, has declared that she will uphold SpaceX’s “zero tolerance” policies regarding workplace harassment.

SpaceX, which Musk founded in 2002, has been a key player in the American space program. It is the only organization capable of sending NASA astronauts into space from American soil and has plans to take astronauts to the moon for NASA within the next ten years.

SpaceX is also one of two companies on which the Pentagon depends to launch into space the bulk of U.S. military and spy satellites.