Superintendent Carol Johnson is taking a leave of absence after the death of her husband Matthew late Monday. The chief financial officer of the school system, John McDonough, will take over as acting superintendent.

Matthew Johnson, who was married to Dr. Johnson for nearly 40 years, passed away in Memphis, Mayor Thomas Menino and School Committee chair Michael O’Neill said in a letter sent out to staffers on Tuesday morning. “Our hearts go out to the Superintendent and her family during this extraordinarily difficult time,” they wrote. “We all know how lucky we are to have a leader who considers the people who make up our schools as part of her family. This morning, we know our entire community is grieving alongside her.”

Menino and O’Neill wrote that the Johnson family “shares a powerful sense of civic responsibility, educational equity and a commitment toward creating better opportunities for all. “

Dr. Johnson has served as superintendent since 2007. She previously served as superintendent in Memphis and Minneapolis.

McDonough, the acting superintendent, has served as the chief financial officer for Boston public schools since 1996.