MARBLEHEAD – A pre-existing medical condition may have played a key role in Saturday’s drowning death of a Peabody man off Marblehead Neck, said Marblehead police spokesperson Lt. David Millett.Robert D. Cunningham, 31, was pronounced dead a short time after being pulled from the water between Marblehead Neck and Tinker’s Island at about 12:10 p.m.Cunningham was alone and fishing in a kayak without wearing a life preserver when he fell into the water, police said.In a press release issued Saturday, Millett hinted Cunningham might have fallen due to a seizure.”The preliminary investigation indicates that Mr. Cunningham had a medical history involving seizures and may have suffered such an event while fishing from his kayak, causing [him] to fall into the water,” Millett said.Rescuers responded to the water after receiving a 911 call from a resident of Sergeant Road.Marblehead, Salem and Beverly harbormasters, Marblehead police and fire along with local boaters assisted in pulling Cunningham from the water.According to police, CPR was administered on Cunningham while he was transported to Clark Landing and brought to Salem Hospital, where he was pronounced dead.On Wednesday, three people were rescued fishing in the same waters when their canoe flipped around 10:30 p.m. The victims were not wearing life jackets as they fished off Riverhead Beach.