"Our family is grieving along with all those who have been affected by this enormous tragedy," said Peter Lanza in a statement Saturday night. "No words can truly express how heartbroken we are. We are in a state of disbelief and trying to find whatever answers we can."
His son Adam Lanza, 20, is suspected of opening fire on the Sandy Hook Elementary School in Newtown, Conn., on Friday, killing 20 children and six adults before taking his own life. Adam's mother Nancy Lanza also was killed earlier at another location.
The Lanzas were divorced in 2009. Nancy's family also released a statement:
"The family of Nancy Lanza share the grief of a community and a nation as we struggle to comprehend the tremendous loss that we all share. Our hearts and prayers are with those who share in this loss. On behalf of Nancy’s mother and siblings we reach out to the community of Newtown and express our heartfelt sorrow for the incomprehensible and profound loss of innocence that has affected so many."
Peter Lanza and Adam's older brother Ryan were questioned by the FBI but are not suspects, a law enforcement source tells PEOPLE.
The last of the bodies were removed by early Saturday as police narrowed in on a motive and released the names of the victims.
Investigators have found "very good evidence ... as to how, and more importantly, why, this occurred," State Police spokesman Lt. J. Paul Vance told reporters. He didn't elaborate.