The runner who collapsed and died during the Brighton marathon on Sunday has been named as 23-year-old Sam Harper Brighouse.
Sam, from Forest Hill, London, suffered a suspected cardiac arrest on Grand Avenue in Hove, 16 miles into the race.
Friends, strangers and fellow marathon runners also left messages of condolence on the site.
One read: "I'll be running in Sunday's London Marathon and will spare a minute in thought. RIP."
His father, Richard, told the Evening Standard: “He loved sport. He trained really hard and was as fit as a fiddle. We are mystified, he has always been into sports like football and basketball and was very healthy.
“We went as a family to watch the marathon. He had a tracker on but it stopped working half-way through the race. We thought the tracker had failed but then received a call at the finishing line saying he had collapsed. We just cannot believe it. We are devastated.
“The emergency services and hospital did all they could.”
A spokesman for organisers of the marathon said on Sunday: "It is with regret that we can confirm that a competitor collapsed and later died competing in the Brighton Marathon this morning.
"Our emergency plans were put in place and he was treated at the scene by senior doctors, nurses and paramedics before being taken by ambulance to hospital.
"Despite receiving immediate attention, the runner was later declared dead at the Royal Sussex County Hospital."
He added: "We at Grounded Events, the organisers of the Brighton Marathon, would like to express our sincere condolences to family and friends of the deceased."
A post mortem examination will take place on Monday.
England cricketer Matt Prior had officially started today's race, the fourth Brighton marathon, in Preston Park at 9am.
Organisers said 9,315 competitors were taking part.