"There's nothing about any of this that is normal," the freshman Democrat said on CNN's "The Lead with Jake Tapper."
Harris said Deputy Attorney General Rod Rosenstein's memo did not provide a real case for President Donald Trump firing FBI Director James Comey.
"If someone gave me that memo as a basis for firing the chief investigator of a case, I would say send it back and start again," Harris said.
She said an effective memo would have to have more substance as well as cite case law and Department of Justice regulations.
As for Rosenstein's boss, Attorney General Jeff Sessions, Harris repeated her call that he should step down.
"I think Jeff Sessions should resign," Harris said. "There is good reason to believe that he was not truthful when he testified before Congress. ... Then just in the last 48 hours that he would sign off on firing the person who is investigating the case he's recused from calls into question his objectivity and his ability to keep his word."
Harris had previously called
for Sessions' resignation following reports that he had met with Russian Ambassador Sergey Kislyak last year.
Sessions said he would recuse himself from all matters relating to the 2016 campaign, although he joined Rosenstein in recommending Trump fire Comey.
Comey announced publicly in March that the FBI was investigating potential collusion between Russia and Trump associates. Harris is a member of the intelligence committee, which also has an ongoing investigation into the matter.
Harris said Comey's firing was connected to that investigation and called for a special prosecutor or independent commission with subpoena power to head the executive branch's criminal inquiry.
"If we connect the dots, there is a nexus between the Russia investigation and the firing of Comey," Harris said.