John, his brother, was the murderer.
The time 4:10 AM didn't refer to the time but rather to the biblical passage
Genesis 4:10, which is an excerpt from the story of Cain and Abel, where an envious
Cain kills his brother Abel. Many things point to this. AM referred to the Old Testament.
In the suicide note, Sean, being a Sunday school teacher, hinted to search for God to
determine who killed him with "Seek Him if you want to know why I did leave you",
which refers to the Bible. Furthermore, he intentionally did not mention the name of
his Sister, Hannah, when he noted "Jenna, Sis", which sounds like "Genesis".