American athlete Torrin Lawrence has been killed in a car accident, aged 25.
Lawrence's car suffered a puncture on Interstate 75 near the state border between Georgia and Florida and as he waited for the emergency services, his vehicle was hit by a truck.
Crisp County Sheriff Billy Hancock told NBC: "We're not exactly sure where he was in relation to the car (but) he was caught up in the accident."
Lawrence ran in the heats as the United States won 4x400 metres gold at the IAAF World Relays in Nassau, Bahamas, in May and finished ninth in the individual 400m at the US Outdoor Championships in June.
US sprinter Allyson Felix led the tributes on Twitter, writing: "Sad to hear about the passing of Torrin Lawrence. My prayers go out to his family & friends. We lost a talented member of our track family."
Jeremy Wariner wrote "RIP @TrackTarantula" - referring to Lawrence's Twitter identity - while Britain's Martyn Rooney added: "Sad news about Torrin Lawrence, solid athlete".
Perhaps the most poignant tribute came from fellow American 400m runner Manteo Mitchell, who wrote: "This can't be real life man. Just talked to him yesterday man.... RIP Torrin! See ya up there one day. Prayers w/fam
"It's sad that it takes tragedy to really make you realize just how special time with people we care about really is!"