A man and woman in their 60s told officers they were at the Castaway Island Preserve near San Pablo Road South and Beach Boulevard around 3:15 p.m. Sunday when they were attacked by a young man with a baseball bat.
The woman told Channel 4 they asked him what he was doing and started to call 911 when he attacked them.
She said the man punched and kicked her fiance, causing him to lose consciousness. She says he also kicked her in the back of the head.
Police said the woman was okay but the man had to be rushed to the hospital.
The woman said she wasn't sure but she didn't think her attacker used the baseball bat on them.
The woman's daughter said she's lucky they weren't killed.
"That park is a place where a lot of women go by themselves to go walk their dog," she said. "I wouldn't recommend anyone going out there alone. [My mother] is just having a recurring of the scene."
Police used K-9s and a helicopter to look for the suspect, but didn't find anyone. On Monday, 3 officers were patrolling the city-owned park for safety.
Danielle Maske and her husband were at the preserve Monday afternoon, and said they hadn't heard about the attack, but it's very frightening.
"It's definitely out of left field, I mean you are the first person who told me about it," said Maske. "Hearing about it definitely gives me cause for concern."
The man attacked was released from the hospital later Sunday, but had a very visible black eye, cuts and bruises on his face.
The couple said the man did not try to steal anything from them and was very well-dressed.
Anyone with information about the attack is asked to call the Jacksonville Sheriff's Office at 904-630-0500 or First Coast Crime Stoppers at 1-866-845-TIPS (8477).