Costa Rica defender Marshall killed in car crash
"It's incredible, I can't believe it... you never know what's going to happen to you tomorrow, but that's life," agent Jorge Ulloa told a local radio station.
The 25-year-old Marshall, who played for Danish club Aalborg, died in a head-on collision with a truck on a mountain highway in eastern San Jose, local media quoted the Red Cross as saying.
"He was a young man with a bright future, well loved for his easy-going nature... we're all shocked, it's a blow," said Costa Rica's Argentine coach Ricardo La Volpe.
Marshall equalised in Costa Rica's Gold Cup quarter-final against Honduras on June 18 with his first goal for his country. The match ended 1-1 and Honduras won a penalty shootout.
"This is a terribly sad day," Aalborg coach Kent Nielsen told the club's website.
Kenneth Emil Petersen, who roomed with Marshall, added: "Dennis was a fantastic person. He had a fantastic sense of humour. What has happened is so unreal."
Marshall's wife Arianna also died in the accident.