ProPublica fact-checked White House press secretary Sean Spicer in a flurry of tweets Monday after he accused the site of harboring a liberal bias.

ProPublica, which describes itself as “an independent, nonprofit newsroom that produces investigative journalism in the public interest,” did not appreciate Spicer calling it a “left-wing blog” during the Monday press briefing and responded on Twitter

1/ So @seanspicer just called us a “left-wing blog.” Since we’re actually in the biz of facts, we figured we’d respond w/ a few... — ProPublica (@ProPublica) April 3, 2017

The Pulitzer-prize-winning news site accused Spicer of trying to undermine its credibility after publishing a report earlier in the day revealing that Trump can draw money from his business-linked trust at any time with no requirement to disclose it.

.@seanspicer 2/ @seanspicer was trying to knock our story that Trump’s trust doc was revised to say he can take $ frm biz anytime https://t.co/xcohyMmoRc — ProPublica (@ProPublica) April 3, 2017

ProPublica’s report said the withdrawal language was the biggest change in his trust policy, inserted about a month after the original documents were signed.

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“Trump can draw money from his more than 400 businesses, at any time, without disclosing it. The previously unreported changes to a trust document, signed on Feb. 10, stipulates that it ‘shall distribute net income or principal to Donald J. Trump at his request’ or whenever his son and longtime attorney ‘deem appropriate,’” the report reads.

Spicer denied any changes to the president’s trust withdrawal policy and defended the use of the trust, reasoning that withdrawing money is the purpose of a trust. Then Spicer slammed the credibility of ProPublica.

ProPublica tweeted contrasting photos of the documents in question.

The site asserts it had asked the White House and Trump Organization to explain the changes in the trust, but said it received no response.

.@seanspicer 5/ We do no-surprises journalism. We told the Trump Org & WH what we knew and gave them time to explain.They didn’t. https://t.co/pYfcdEp64W pic.twitter.com/paZfZWr4W1 — ProPublica (@ProPublica) April 3, 2017

ProPublica reiterated its mission to be a check on power and hold people accountable.

.@seanspicer 6/ What we do is hold people in power accountable, no matter who they are, or what names they call us. We do it with facts. Like... — ProPublica (@ProPublica) April 3, 2017

ProPublica tweeted multiple previous reports as examples of its fact-checking the Trump.

.@seanspicer 7/ The fact that Tom Price bought drug company stock same day he pushed policy that could help the company. https://t.co/nica3s6oi1 — ProPublica (@ProPublica) April 3, 2017

Its twelfth tweet said the organization had also served as a check on the Obama administration.