Mayor Martin Walsh has appointed Deputy Chief Joseph Finn as Boston's next fire commissioner.

Walsh made the announcement Monday at fire department headquarters. Finn, a 29-year department veteran and former Marine, will be officially sworn in later. He succeeds Interim Commissioner/Chief John Hasson who filled in after Roderick Fraser Jr. stepped down in January after seven years.

The city says Finn, 53, of Quincy, has served the department in a variety of roles, including helping develop state regulations for the use of semi-automatic external defibrillators. Since 2005, he has commanded the fire division covering the Allston-Brighton, Charlestown, East Boston, Back Bay and South Boston neighborhoods.

Finn was also incident commander during the March fire in Back Bay that killed two city firefighters.

In March, Boston Public Radio hosts Jim Braude and Margery Eagan spoke with then-deputy fire chief Joseph Finn. Listen to their interview here.