The Highlands County Sheriff's Office said the attack happened sometime between 9 a.m. and 1 p.m. Thursday at the victim's home on Ramona Avenue near State Road 17.
Deputies said the 88-year-old man suffered critical injuries and had to be airlifted to a trauma center following the attack.
"The incident was not a random attack and there is no danger to the community at this time," the sheriff's office said.
According to investigators, a person of interest is in custody on unrelated charges.
Anyone with information is asked to contact the Highlands County Sheriff's Office at 863-402-7250, or call Heartland Crime Stoppers at 1-800-226-TIPS.