Robert DeLeo, the longest-serving House speaker in Massachusetts state history, announced Monday that he will be formally stepping down Tuesday.

DeLeo said in a letter to the House Chamber that he would be leaving his post this week, according to NBC Boston. This ends his 12-year tenure, during which he oversaw legislation surrounding gun control and criminal justice, as well as the legalization of casino gambling in the state.

“It has been an honor and a privilege serving as a member of this institution for almost 30 years,” DeLeo wrote in the letter. “The faith and trust my colleagues placed in me by electing me as their Speaker for a record 6 consecutive terms fills me with a profound sense of gratitude and appreciation. My pride with what we have collectively accomplished over the last 12 years will never be diminished.”

DeLeo is expected to take a job at Northeastern University, his alma mater, according to Boston.com.

Northeastern University did not disclose what role Mr. DeLeo would be filling, but stated on Monday, “pending ongoing conversations, we are looking forward to welcoming Speaker DeLeo back to his alma mater.”

The House will be able to choose a new speaker before the next session begins, and a Democratic caucus is expected to meet Wednesday to elect a new speaker.

Ron Mariano, 74, is the likely successor to DeLeo, appearing to have secured the votes necessary to become the next Massachusetts speaker.

. @SpeakerDeLeo will leave office with an impressive list of accomplishments. I look forward to celebrating his achievements tomorrow as he bids farewell to the House of Representatives.

— Ron Mariano (@RonMariano) December 28, 2020

“I will be a candidate for Speaker at this week’s Democratic Caucus and I am confident that my colleagues will elect me to lead the House through the remaining days of session,” Mariano said.

In his resignation letter, DeLeo noted that he believes that the Massachusetts House is poised for “continued success” after he vacates his position.