Facebook CEO Mark Zuckerberg admonished his staff for repeatedly crossing out the slogan, “black lives matter,” and replacing it with “all lives matter” on the company’s wall at its Menlo Park headquarters in California, US.

“There are specific issues affecting the black community in the United States coming from a history of oppression and racism. ‘Black Lives Matter’ doesn’t mean other lives don’t — it’s simply asking that the black community also achieves the justice they deserve,” Zuckerberg wrote in an internal Facebook post, as quoted by the Independent.

Zuckerberg expressed disappointment at his employees’ continued behaviour in spite of his “clear communication” that such behaviours are not acceptable. He discussed this during a question and answer session last week.

“Despite my clear communication at Q&A last week that this was unacceptable, and messages from several other leaders from across the company, this has happened again,” he wrote. “I was already very disappointed by this disrespectful behaviour before, but after my communication I now consider this malicious as well.”

Zuckerberg also sought to clear out misconceptions around the movement that rose following the shooting of unarmed black teens Trayvon Martin in 2013 and Michael Brown in 2014. The message was concluded by noting that the experience was “hurtful” to the black community and that his employees should make efforts to investigate it.

“I hope and encourage people to participate in the Black@ town hall on 3/4 to educate themselves about what the black lives matter movement is about.”

The phrase “black lives matter” was first devised by activist Alicia Garza in a Facebook post, in response to Martin’s killing. It became the slogan of resurgent civil rights movements against police killings of unarmed black men across the US, the Guardian reported.

“Not just all lives. Black lives. Please do not change the conversation by talking about how your life matters, too. It does, but we need less watered down unity and a more active solidarities with us, Black people, unwaveringly, in defense of our humanity,” Garza wrote in 2014.

According to an internal report of 2014 by Facebook, only 2 percent of its employees are African-American.