The parents of Adam Lanza, identified as the gunman in the mass shooting Friday at Sandy Hook Elementary School, divorced in 2009 after 28 years of marriage because their relationship had “broken down irretrievably,” court records show.

Nancy Lanza was afforded a comfortable life under the terms of the divorce. She had no income at the time the marriage was legally dissolved, in September 2009. Her ex-husband, Peter Lanza, earned an annual salary of nearly $445,000 as an executive at General Electric and agreed to pay annual alimony of $240,000.

That figure was scheduled to increase steadily for cost of living considerations, and Nancy was due to receive $289,800 in 2012, court records show.

Police say Adam fatally shot his mother at their home in Newtown, Conn., on Friday morning before driving to Sandy Hook and gunning down 20 first-graders and six members of the school’s staff, then turning a gun on himself.

According to court records, Peter and Nancy Lanza married in June 1981 in Kingston, N.H.

Read the stories of the Newtown shooting victims

The couple had two children. Ryan Lanza was 21 years old when his parents divorced three years ago, and Adam was 17. The Lanzas agreed to joint custody of Adam, with his primary residence at the house in Newtown with Nancy. Peter, who lived in Stamford, was afforded “liberal visitation and vacations.”

The Lanzas’ divorce agreement contained no details about what led to the couple’s divorce or the family dynamics. Peter gave a brief statement shortly after the murders but has not granted any interviews.

Before their divorce could be granted in Connecticut Superior Court, Nancy and Peter Lanza were required to complete a state-mandated parenting education program, which they did in the spring of 2009.

The couple divided their material assets in a “fair and equitable manner,” court documents say. Both retained bank accounts, investments and retirement assets in their respective names. Peter kept his vehicle, a 2003 Nissan Altima, and Nancy kept the house on Yogananda Street in Newtown.

They were joint owners of two renewable tickets for nine Boston Red Sox baseball games each season, and the Lanzas agreed to a five-four split that alternated each year.

Peter was responsible for health insurance costs and agreed to solely finance the college costs for both children. He also agreed to provide a car for Adam, “if and when he shall wish to have one,” according to the agreement. Nancy was to be responsible for insurance and maintenance.