Though Rosenstein did not explain what prompted the statement, many political observers connected it to recent reports that special counsel Robert Mueller, who is leading the DOJ investigation into Russian election meddling, is also investigating whether Trump attempted to obstruct justice.
Mr Mueller was appointed as special counsel to investigate Moscow's involvement in the presidential election previous year and possible collusion by Trump campaign associates with the Russians, but there has been no indication that Mr Mueller told the president to fire Mr Comey.
"Witch hunt' is how Trump characterises the probe into Russia's election interference and possible ties to his campaign associates".
If Mueller is investigating Trump's firing of Comey as possible obstruction of justice, he might want to learn about Trump's interactions with Rosenstein, the Justice Department official who wrote the memo criticizing Comey's performance before his firing.
And, as it turned out, the FBI had already launched its own obstruction investigation days after the firing - right after Trump went on NBC and himself linked Comey's firing to "this Russian Federation thing".
He appeared to be referring to Rod Rosenstein, deputy attorney general who is now leading the probe.
To the contrary: Thanks to The Washington Post, we now know that collusion is only one of three subject areas that the FBI investigation, now led by special counsel Robert Mueller, is exploring.
Comey told Congress last week that before being sacked, Trump pressured him to drop an investigation into his former national security advisor, Mike Flynn, who was forced to quit for lying about his links to Moscow.
ABC's report comes as Trump said on Friday he is personally under investigation in the widening Russian Federation probe, over Comey's firing.
More news: Tapwrit wins Belmont StakesThe investigation, the president added is being led by "very bad and conflicted people".
Other presidents have managed to compartmentalize investigations and go about the business of governing, but Trump seems consumed by the Mueller probe.
The latter being Trump's effort (dutifully followed by his media groupies) to slime Mueller and the talented legal team he has assembled.
The tweet on Friday was the first official confirmation by Trump that he himself is under investigation.
As the investigation expands, that raises the possibility that Rosenstein may recuse himself from that role, since he wrote the memo justifying Comey's firing. Mueller has not made any public comments about Comey amid the firestorm.
Trump also lashed out at the media on a day that aides had hoped would be focused on his decision to undo some of former President Barack Obama's detente with Cuba.
A Justice official said Rosenstein was motivated in part because of frustration that recent news stories have unfairly brought on a torrent of "leak" accusations against the Federal Bureau of Investigation and Mueller's team.
Confidants and advisers close to Mr Trump said his fury was mounting at the probe and he had been yelling at TV sets about its press coverage.
/cdn.vox-cdn.com/uploads/chorus_image/image/55193127/unc_field.0.jpg "Reds draft high school star Hunter Greene 2nd overall in MLB Draft")
