The pedestrian was struck around 11:15 a.m. in the 100 block of North Avenue 61, and died at the scene, according to Brian Humphrey of the Los Angeles Fire Department.
The fatally injured man was in his 30s, said coroner's Chief Craig Harvey. His name was not immediately released.
Los Angeles Police Department officials said the death was being investigated as a possible suicide.
Joe Lemon of Metro said buses were brought in to shuttle Gold Line passengers between the Southwest Museum and South Pasadena stations. He noted that the Gold Line is Metro's safest rail line, with only two fatalities since it opened in 2003, and both were suicides.