Baltimore County Police identified the man on Wednesday as George Thomas McAleer, 26, of the 1100 block of Quantril Way in Baltimore.
Police believe the man failed to hear the train coming toward him at a high rate of speed after a stolen ATV in his possession "broke down on him next to the tracks just prior to the accident."
Police were called to the 200 block of Philadelphia Ave., which runs parallel to the tracks, about 5:48 p.m. and located a body on the tracks, said Lt. Rob McCullough, a county police spokesman.
Police remained on the scene for hours. At the peak of the investigation, two MARC trains and six Amtrak trains were stopped, waiting to pass.
Paulette Austrich, a spokeswoman for the Maryland Transit Administration, said two of four tracks in the area reopened shortly before 8 p.m. and trains began moving again at reduced speeds.
It remained unclear Tuesday night which train had struck McAleer, rail officials said.
Marc Magliari, an Amtrak spokesman, said shortly before 9 p.m. that Amtrak had "not found any evidence of a trespasser strike," but was checking its equipment for signs, as were other rail operators.
"We have no reports of making contact with any trespassers or pedestrians," he said. "If we do find something we will of course turn something over to Baltimore County."
In recent months there have been several other deaths on railroad tracks around Baltimore, all of them suspected suicides, according to police.
In a statement, Baltimore County Police said the death Tuesday "highlights the danger of people trespassing upon railroad property."