"He walked to me, accusing, f-word, f-word, f-word, and pulled the gun," Vilkin told KGTV from jail. "I pulled out my gun, and I was ready for it, and I shot him. It was self-defense."
According to investigators, Upton may have pulled out a cell phone, but there was no other gun found at the scene.
Next year, it will be a jury's job to decide whether Vilkin is an obsessed landowner who snapped and deliberately killed his own neighbor or if he was a terrorized intellectual, driven to defend himself against repeated verbal threats.
Meanwhile, Upton and Vilkin's families are both still feeling the effects of what transpired between the two neighbors.
"Who is this guy," Upton's daughter, Elizabeth Upton, asked, "this man who murdered my father in cold blood? For what?"
Upton's wide-reaching charity work inspired his children to follow in their father's footsteps. Both Johnny and Elizabeth Upton have traveled extensively to help orphans abroad.
Elizabeth Upton makes documentaries for a non-profit group her father started called Media4aCause, which provides short documentaries and brand training to worthy causes and charities for free, and Johnny Upton works in Uganda. Both said their work is a way to feel closer to their father.
Tamara Vilkin wishes he never bought the land for her "because it brought nothing but pain to us."
Tune in to see the full story on ABC News' "20/20" on Friday, Sept. 20, 2013, at 10 p.m. ET.