Police said the incident happened in Titusville during an argument over a television show.
Officials told WFTV that after the argument, Stuart Womack began throwing items at his grandfather, William Womack.
Investigators said after Stuart Womack punched his grandfather, he began beating him with a yardstick, using enough force to break his ribs.
Police said the confrontation then went outside, where William Womack was pushed to the ground. Investigators said Stuart Womack told them he then threw his hammer at his grandfather three times.
William Womack was taken to the intensive care unit to treat his injuries but later died.
Stuart Womack faces a preliminary charge of second-degree murder.