Sean Spicer filled 'notebook after notebook' on Trump campaign and White House meetings - and it could have major implications for the Russia investigation

Associated Press/Andrew Harnik

White House press secretary Sean Spicer takes notes as President Donald Trump and NATO Secretary General Jens Stoltenberg hold a news conference in the East Room at the White House in Washington, Wednesday, April 12, 2017, in Washington.

Sean Spicer, the former White House press secretary and Republican National Committee spokesman, was reportedly well-known for being a copious note-taker during his time working on the Trump campaign and later at the White House - a habit that could prove relevant as special counsel Robert Mueller's investigation heats up.

Axios reported on Thursday that Spicer filled "notebook after notebook," to the extent that his subordinates joked that he would eventually write a tell-all memoir, according to Spicer's former colleagues.

"Sean documented everything," one source familiar with Spicer's note-taking told Axios.

Spicer's name has already been floated as a potential witness Mueller may pursue. The Washington Post reported earlier this month that Mueller has already alerted the White House that he will probably seek to interview Spicer, along with five other current and former Trump associates.

The associates are thought to have been present during internal discussions of interest to Mueller's investigation into Russian interference in the 2016 election and possible collusion with the Trump campaign.

Thorough note-taking is a departure from typical White House practice - officials from previous administrations told Axios that they deliberately took scant notes during their time in the West Wing due to past investigations.

Another White House official told Axios that "people are going to wish they'd been nicer to Sean … He was in a lot of meetings."

When questioned by Axios reporter Mike Allen about his notes, Spicer reportedly grew irate and accused Allen of harassment.

"Please refrain from sending me unsolicited texts and emails," Spicer told Allen in an email. "Should you not do so I will contact the appropriate legal authorities to address your harassment."