Railroad spokesman Gus Melonas in Seattle says it happened at 11:40 p.m. Thursday.
He says the train was traveling from Seattle to Portland when it hit a person trespassing on BNSF Railway property about three miles south of Tacoma, in the Titlow Beach area.
Melonas says the incident shut down the line for about two hours and delayed two trains. There were no injuries to the train crew.
Melonas says the person was the 14th to be struck and fatally injured by a train on BNSF property this year.
BNSF Railway is investigating.