ABC News(WASHINGTON) -- A staffer on 2020 candidate Tom Steyer’s campaign downloaded volunteer data that belonged to fellow presidential hopeful California Sen. Kamala Harris' South Carolina campaign operation, according to the Democratic National Committee, which issued a cease and desist letter for breach of access Saturday.

The Steyer campaign staffer was identified as Dwane Sims by both the Steyer campaign and Democratic National Committee to ABC News.

Steyer's campaign said Sims accidentally downloaded Harris' files thinking they belonged to their own campaign. He then alerted the DNC that he had access to the data, a spokesperson on the Steyer campaign said.

Call information and logs of when the files were downloaded obtained by ABC News from a source with direct knowledge show Sims phoned the DNC at 2:56 p.m. on Friday for a 12-minute call, but the data wasn't downloaded until 3 p.m. -- during the call, not prior to it. it is unclear from the logs when exactly the request to download information was made.

The logs also show that "Harris" is written prominently on the files.

When asked if he deliberately accessed data from the Harris campaign, Sims told ABC News in an exclusive interview, “absolutely not,” calling the accusation a “false narrative."

“I did not steal data. There was a data breach, which is common. Whether it's your credit card information or your social security number, these things happen. I felt like I took the appropriate action immediately," he said. "However, this incident is painting the campaign in such a bad light that I would rather step away then hurt Tom's chances of really doing something phenomenal. It’s more about the nation and doing the right thing ... But I think the people who know me, know that I'm not going to do anything immoral,”

Sims was placed on administrative leave from the campaign over the weekend, per senior Steyer aides, and the state party banned him from the voter file and all party systems.

As news broke of the breach Monday night, the Steyer campaign announced that Sims had resigned.

"When we first learned about the matter, we conducted an internal investigation and wiped Mr. Sims' computer to make sure the data was completely deleted and that there was no access to other campaign data. We understand the sensitivity and importance of this information," campaign manager Heather Hargreaves said in a statement.

"We apologize to the South Carolina Democratic Party and the DNC. Tom Steyer and the Steyer campaign extend our deepest apology to Senator Kamala Harris and her campaign,” she added.

Steyer echoed this apology in a tweet soon after, and said he had reached out personally to Harris.

"I was deeply disappointed to learn of this situation and have personally reached out to @KamalaHarris," he wrote. "To every organizer who is putting in the work for a candidate they believe in: I'm grateful for your efforts. Your hard work is what will defeat Donald Trump in 2020."

The DNC said it does not intend to file charges.

“It is being labeled as unethical and in violation of our policy,” DNC communications director, Xochitl Hinjosax told ABC News. “He downloaded information for another campaign, and then he was forced to delete. I will leave it to others to decide what they want to call it, but it's definitely unethical.” she added.

The Harris campaign, which owns the data, declined to comment when asked whether charges would be pressed.

Prior to joining the Steyer campaign, Sims worked as the voter file manager at the South Carolina Democratic Party.

According to the state party, after leaving his post, Sims "maintained a separate user account, which is in clear violation of the VoteBuilder protocol." VoteBuilder is a software program used by Democratic campaigns to combine data and reach voters.

Sims told ABC News his profile was deleted when he left his position at the state party to join the Steyer campaign.

Rep. Gilda Cobb Hunter, D-South Carolina, who serves as a member of the DNC executive committee, tells ABC News that there have been security “issues” with the party’s voter database in “previous cycles.”

Harris' campaign reacted to the accusations following the reported revelations, lauding its own work in South Carolina.

“Our organizers and volunteers work incredibly hard, and as this story notes, our campaign "has built a particularly extensive field organizing operation in South Carolina." It's unfortunate anyone would try to steal that work from our team,” said Ian Sams, Harris’ national press secretary.

During a call announcing an endorsement from the Higher Heights for America PAC, Harris called the incident “deeply unfortunate” adding that her organizers "work hard" and “folks have recognized the value of [her campaign's] list.”

"Our South Carolina team has been on the ground for many, many months, really putting around-the-clock work into organizing and building our list," Harris told reporters. "It's organizers who are paid and volunteers who believe in our campaign, believe in our message and have been building up what is one of probably the greatest assets of the campaign."

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