Robert Kimutai Ngeno was leading the 38th Buenos Aires marathon with just 4km to go in the Argentinian capital last Sunday.
The Kenyan marathoner had passed through the halfway point in 1:03.21 after taking the lead at the 25th-kilometre mark.
Kimutai Ngeno led through kilometre 38 before disaster struck.
A crazy dog appeared out of the blues, lunged at him, and chased him off the road.
A small crowd in the street intervened to help the Kenyan runner and chased the dog away.
But it was too little too late. He lost pace and concentration from that point onwards.
The 29-year-old, trained by Willy Langat at the Kelite altitude training camp in Nakuru, resumed the race but could only manage a third-place finish behind his compatriots Cornelius Kiplagat (first with 2:08.29) and Paul Kipngetich Tanui (second in 2:09.57).
Kimutai finally crossed the line in a time of 2:10.16, third and frustrated.
He missed out of a substantial KSh 1.1 million (USD 7,450) prize money.