Mark Zuckerberg had strong words for Facebook employees after finding out that someone has been crossing out "Black Lives Matter" on the walls at the company's Menlo Park, California, headquarters.

In an internal message shared with employees and obtained by Gizmodo, the CEO described repeated instances of the phrase "black lives matter" being crossed out and replaced with "all lives matter."

Zuckerberg noted he had previously addressed the issue with employees at a Q&A and said he now considered its continued occurrence "malicious."

“‘Black lives matter’ doesn’t mean other lives don’t — it’s simply asking that the black community also achieves the justice they deserve,” he wrote. "We've never had rules around what people can write on our walls — we expect everybody to treat each other with respect."

You can read his full message to employees below.

Image: Gizmodo

The walls at Facebook's headquarters in Menlo Park are adorned with motivational posters and handwritten messages, including by Black Lives Matter activists, who visited the campus a week ago.

BLM Sacramento with BLM Bay Area and Color of Change at a meeting with Facebook A photo posted by Black Lives Matter Sacramento (@blmsacramento) on Feb 11, 2016 at 10:36pm PST

#Facebook knows what's up! Love the posters up around campus! #BlackLivesMatter #BLM #FBHQ #Facebook #FacebookHQ A photo posted by Matthew Sena (@matthewslife90) on Feb 25, 2016 at 9:37am PST

Facebook, like other Silicon Valley companies, has struggled with diversity. According to the company's most recent data, just 2% of its U.S. employees are black.