Schmidt, who was pregnant, was pronounced dead at the scene, as was her 19-month-old son, Kaleb. Four-year-old Weston and 6-year-old Owen died days later.
Woulfe has been in custody since deciding to plead guilty after his trial ended in a mistrial last March.
At sentencing, Woulfe told the court: “From the bottom of my heart, I am sorry. … I know the Schmidt family never plans on forgiving me or not hating me, but I hope they know how sorry I am.”
The Rev. Frank Italiano, pastor of Trinity Lutheran Church in Crete, shared a statement from Lindsey Schmidt’s mother, Tammy Riechers, who wrote: “After five long years, you have lied and denied everything. What you have done is unforgivable.”