JEFFERSON CITY, Missouri - Gov. Greitens announced his resignation at a press conference Tuesday afternoon. Greitens, who faced possible impeachment over an extramarital affair and allegations of misuse of a charity donor list for political purpose, said he will resign effective this Friday at 5 p.m. local time.

The 44-year-old's brief press conference addressed the investigations and the toll it has taken on him, his family and friends.

"I came to office to fight for the people of Missouri ... I am thankful to all those who have worked beside me, who sweated beside me, those who gave their time, their energy and their precious resources, so that we could pursue our mission of taking Missouri in a new and better direction," he said. "The last few months have been incredibly difficult for me, for my family, for my team, for my friends and for many, many people ... This ordeal has been designed to cause an incredible amount of strain on my family ... endless personal attacks designed to cause maximum damage to family and friends."

"We must -- as we have always done -- work to improve the lives around us ... I will always be a fighter for the people of Missouri. The time has come to tend to those who have been wounded, and to care for those who need us most," Greitens said emotionally.

Even while resigning, he remained defiant.

"I am not perfect. But I have not broken any laws or committed any offense worthy of this treatment," Greitens said. "I will let the fairness of this process be judged by history."

Greitens didn't take any questions from reporters after his brief statement. He took the oath as Missouri's chief executive nearly 17 months ago with a pledge to root out "corrupt career politicians."

He was involved in an affair with his former hairdresser. He had been considered a rising star in the Republican Party and spent nearly six months fighting to stay in officer after that affair became public in January during a TV news report that aired immediately following his State of the State address. The probes into his conduct by prosecutors and lawmakers began with allegations stemming from the affair and expanded to include questions about whether he violated campaign-finance laws. 

Missouri Attorney General Josh Hawley says Greitens "has done the right thing" by announcing his resignation.

Republican leaders in the Missouri House say GOP Gov. Eric Greitens has "put the best interest" of the state's residents first in deciding to resign.

House Speaker Todd Richardson, Speaker Pro Tem Elijah Haahr, and Majority Leader Rob Vescovo issued a joint statement Tuesday, moments after Greitens announced he was stepping down Friday.

They said as public servants, their duty is to put the best interests of the people first and, "The Governor's decision today honors that duty and allows Missouri to move forward."

The three leaders also pledged to help ensure a smooth transition to power for Lt. Gov. Mike Parson as he takes over for Greitens.

They also thanked members of a special House investigatory committee and said for their "serious and professional" manner.

Hawley, like Greitens a Republican, said in a brief statement that he wished Parson well as he prepares to make the transition to governor. Hawley says he stands ready to assist in the transition. Hawley is running to unseat Democratic Sen. Claire McCaskill.

The Associated Press contributed to this report.