"Over the past two weeks, senior campaign leadership received multiple complaints regarding inappropriate behavior by Rich McDaniel," Warren campaign spokeswoman Kristen Orthman told Fox News. "Over the same time period, the campaign retained outside counsel to conduct an investigation."
McDaniel served as the campaign's national organizing director.
"Based on the results of the investigation, the campaign determined that his reported conduct was inconsistent with its values and that he could not be a part of the campaign moving forward," Orthman said.
Details of the "inappropriate behavior" were not immediately available, but a source told Politico there were no reports of sexual assault.
McDaniel released a statement saying he'd "separated" from the campaign, according to Politico.
"I have tremendous respect for my colleagues despite any disagreements we may have had and believe departing at this time is in the best interest of both parties," he said. "I would never intentionally engage in any behavior inconsistent with the campaign or my own values. If others feel that I have, I understand it is important to listen even when you disagree. I wish the campaign and my colleagues well."
McDaniel is a veteran of Democratic campaigns, having previously worked as the field and political director for Sen. Doug Jones' successful bid for the U.S. Senate in a 2017 special election. During the 2016 campaign, McDaniel worked as Hillary Clinton's primary-states regional director in the 2016 campaign and was political director for the Democratic Party of Georgia during the first half of 2015.
Fox News' Mike Emanuel contributed to this report.