After high school in Minnesota, Strzok graduated from Georgetown University in 1991, and in 2013 received a master’s degree there. Strzok was an officer in the U.S. Army and then an intelligence research specialist in the FBI.
He has worked at the FBI since the 1990s, is "considered one of the most experienced and trusted FBI counterintelligence investigators", according to The New York Times, and is "considered to be one of the Bureau's top experts on Russia", according to CNN. He served as the deputy head of FBI counter-intelligence and worked on secret matters of espionage involving China and Russia.
Starting on July 10, 2015, Strzok led a team of a dozen investigators to examine Hillary Clinton's use of a private email server. During the investigation, Strzok changed then-FBI Director James Comey's draft language describing Clinton's actions as "grossly negligent" (which may be a criminal offense) to "extremely careless". Strzok and his team helped review newly discovered Clinton emails days before Election Day.
In July 2016 Strzok signed a document opening the FBI's investigation into Russian interference in the 2016 United States elections. He oversaw the bureau's interviews at this time with then-National Security Advisor Michael Flynn. Strzok also became the top FBI agent working for Robert Mueller's special counsel investigation of foreign electoral intervention by Russia in the 2016 U.S. presidential election.
In late July 2017, Strzok was removed from Mueller's team and moved to a human resources position at the agency after reports of text messages transmitted between Strzok and Lisa Page, who worked at the FBI for Deputy Director Andrew McCabe; the text messages appeared to be anti-Donald Trump in nature. According to Strzok's colleagues and a former Trump administration official, Strzok had not previously shown any overt political bias. An associate of his says the political parts of the text messages were especially related to Trump's criticism of the FBI’s investigation of the Clinton emails. Page was assigned to Mueller's investigation as a trial attorney until she left in late September 2017.
Strzok's and Page's colleagues in the FBI said that there was no professional misconduct between Strzok and Page. According to The Wall Street Journal, several agents said that Mueller removed Strzok in order to protect the integrity of the special counsel’s Russia investigation.
Michael E. Horowitz, the Inspector General (IG) of the Justice Department, has an ongoing investigation into how the FBI handled the high profile investigations. Fox News reported that a source close to the probe says it will examine Strzok's participation in various other politically sensitive matters, and that the proble should be done by "very early next year." The IG investigation began in January 2017, and Horowitz expects to issue a report in March or April of 2018. Meanwhile, the Justice Department has agreed to allow the United States House Permanent Select Committee on Intelligence to interview Strzok.