Hartford suffered multiple skull and facial fractures, severe brain trauma, a broken wrist, and optical nerve damage, he said.
A doctor at the Hospital of the University of Pennsylvania, where his son was in intensive care, told him the injuries were consistent with a fall from about 15 to 20 feet, he said. University detectives told him they believe Hartford either fell from a window or had been locked out and was climbing up to get in the window.
Penn officials declined to release information about the fall and issued a one-sentence statement.
"We are deeply saddened by Tom's tragic death, and our thoughts and prayers are with his family and friends at this very difficult time," said Stephen J. MacCarthy, vice president for university communications.
The fraternity also issued a statement, noting that Hartford was a former member.
"While he was no longer affiliated with the chapter, he remained close with many of the undergraduate members," said Brian Warren Jr., executive director. "Our thoughts and prayers go out to his family and friends."
Hartford's father said his son had drinks that evening but was not intoxicated. A child-support system investigator for Monroe County, he said he did not blame the university or anyone and has no plans to sue.
"They've been great to us," he said of the university. "It was just a tragic accident in my mind."
A soccer player and skier, Hartford was a well-liked, positive young man majoring in cognitive science, his father said. Fifty fraternity brothers visited him at the hospital Tuesday.
"They came to say goodbye," Hartford said.
A viewing will be Friday at Clark Funeral Home in Stroudsburg. Services will be Saturday at Reeders United Methodist Church, where Hartford was a member of the youth group.
Contact Susan Snyder at 215-854-4693 or firstname.lastname@example.org, or follow on Twitter @ssnyderinq