“I will stop at Nothing until you, your family, your friends, your entire WORTHLESS LATIN RACE IS RACIALLY EXTERMINATED!” Mr. Lin wrote to the woman on Facebook in June, according to a criminal complaint.

In another message, Mr. Lin wrote to the woman, who was from Spain, that he was acting under the authority of Hitler and God to “DECLARE SPANISH AND ALL SPANISH SPEAKING PEOPLE ILLEGAL.”

In July, he wrote, “I thank God everyday President Donald John Trump is President and that he will launch a Racial War and Crusade.”

Eventually, Mr. Lin began to discuss kidnapping the woman and injuring her co-worker.

He asked an associate to trick her into renting a house, where she would be ambushed, according to the criminal complaint. Mr. Lin said he would pay the associate $25,000 after he drove the chained woman to Seattle, where Mr. Lin was arrested in August. Because she is Hispanic and hates whites, Mr. Lin asserted, “I doubt the F.B.I. would care much about her.”

The messages Mr. Lin sent to the woman came from two Facebook accounts opened under assumed names. But the woman told the F.B.I. she believed that they had, in fact, come from Mr. Lin because he often discussed mass shootings and his admiration for Hitler during his frequent visits to the restaurant where she worked in Key Biscayne, Fla.