Salesforce stock fell as much as 8% on Monday after Insider reported that executive Steward Butterfield is leaving the company in January.

Butterfield is the co-founder and current CEO of the popular workplace messaging platform Slack, which Salesforce acquired for about $28 billion in 2021. Slack saw its popularity boom amid the early days of the COVID-19 pandemic as more and more companies shifted to remote work.

The imminent departure of Butterfield is concerning to Salesforce investors because it marks the third high-profile executive departure in less than a week.

On Wednesday, Salesforce said its co-CEO Bret Taylor would be leaving the company in 2023. That was soon followed up by the departure of Tableau CEO Mark Nelson on Thursday. Salesforce acquired Tableau for about $16 billion in 2019. 

Butterfield said in an internal Slack message viewed by Insider that his departure has nothing to do with the departure of Bret. 

"FWIW: This has nothing to do with Bret's departure. Planning has been in the works for several months! Just weird timing," Butterfield wrote. 

"Stewart is an incredible leader who created an amazing, beloved company in Slack. He has helped lead the successful integration of Slack into Salesforce and today Slack is woven into the Salesforce Customer 360 platform," a Salesforce spokesperson wrote in a statement to Insider.

Slack's next CEO will be Lidiane Jones, who is currently an executive vice president and general manager of digital experiences clouds at Salesforce. The company told Insider that Butterfield was "instrumental" in choosing Jones as his successor. 

The decline in Salesforce stock on Monday of as much as 8% was about quadruple the 2% decline seen in the Nasdaq 100 Index on Monday, and about double the decline seen in the iShares North American Tech-Software ETF, in which Salesforce is the largest holding.