Donald Trump Jr.Donald (Don) John TrumpSarah Huckabee Sanders becomes Fox News contributor PETA billboard in Baltimore calls Kushner a 'rich pest' Dick Cheney to attend fundraiser supporting Trump reelection: report MORE took to Twitter on Sunday to troll House Intelligence Committee Chairman Adam SchiffAdam Bennett SchiffHillicon Valley: YouTube disables 200+ accounts over Hong Kong misinformation | Lawmakers sound alarm over Chinese influence efforts | DHS cyber agency details priorities | State AGs get tough on robocalls | DOJ busts online scammers Nadler asks other House chairs to provide records that would help panel in making impeachment decision YouTube disables over 200 accounts amid protests in Hong Kong MORE (D-Calif.) hours after Attorney General William Barr delivered a summary of special counsel Robert MuellerRobert (Bob) Swan MuellerMueller report fades from political conversation Trump calls for probe of Obama book deal Democrats express private disappointment with Mueller testimony MORE’s investigation to Congress.

As lawmakers from both sides of the aisle reacted following Barr’s summary of Mueller’s lengthy investigation into collusion between the Trump campaign and Russia to interfere in the 2016 election, Trump Jr. knocked Schiff for remaining quiet.

“Has anyone heard from slimy Adam #fullofschiff Schiff today?” Trump Jr. wrote in a post on Twitter Sunday evening. “I mean it must be embarrassing to have have spent the last 2 years as the leader of the tinfoil hat brigade and have it all come crashing down so quick.”

Trump Jr. borrowed the “full of Schiff” reference from his father. President TrumpDonald John TrumpGraham: America must 'accept the pain that comes in standing up to China' Weld 'thrilled' more Republicans are challenging Trump New data challenges Trump's economic narrative MORE has consistently ripped the California lawmaker, who is leading a congressional investigation into Trump.

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Trump’s son added that he is “legitimately concerned for his mental state,” referring to Schiff.

On Sunday morning, before Barr delivered his letter to Congress, Schiff said Congress would have to consider impeaching Trump if Mueller’s report found “overwhelming evidence of criminality” on Trump's part.

According to Barr’s letter, which summarized the conclusions from Mueller’s investigation, there was no evidence of collusion between the Trump campaign and Russia to interfere in the 2016 election.

The letter says that Mueller did not make a conclusion as to whether Trump obstructed justice in the investigation of Russia's election interference, though Barr and Deputy Attorney General Rod RosensteinRod RosensteinSanders, Warren back major shift to fight drug overdoses 10 declassified Russia collusion revelations that could rock Washington this fall Why the presumption of innocence doesn't apply to Trump MORE decided they would not pursue an obstruction of justice charge against Trump.