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A truck driver was charged in newly unsealed court documents with threatening multiple times to assassinate President Donald Trump over the course of more than a month.

Little information about the man, identified as James Anthony Jackson, was made available in a criminal complaint unsealed Tuesday in U.S. District Court in Detroit.

The complaint said only that Jackson is a truck driver and that he was born in 1984.

The documents don't directly say that Jackson is even in custody, but the motion to unseal the case said he was no longer considered a flight risk. No hometown, attorney or court dates were recorded.

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President Donald Trump during a meeting with members of the Senate Finance Committee at the White House last week. Mandel Ngan / AFP - Getty Images

According to an affidavit filed by the Secret Service, Jackson began making rambling, obscene phone calls to Secret Service field offices in Detroit and Chicago on Sept. 17. More calls were made on Oct. 12, 13 and 18, the affidavit said.

In one of the calls, Jackson raged against Trump and said he was going to blow the "white brains out of ... his ... head," according to the Secret Service.

NBC News has redacted the full quotations because of their extreme language.

The Secret Service said Jackson managed to "spoof" the caller ID information transmitted by his phone, making it difficult to track him down. Once agents determined the phone's real number, the Secret Service traced the device to a company called James Jackson Profit Group LLC in Grand Rapids, Michigan.

Contact information wasn't listed for the company, which isn't registered in state business records.

The Secret Service said Jackson used the same phone to harass an unidentified woman who said he called himself "Jamie." According to the Secret Service, "Jamie" threatened to "cut off her head and parade it in front of the White House for Trump."

Relatives of Jackson told investigators that they had lost contact with him for about a year until he started making harassing, threatening calls to them, as well.

If he's convicted, Jackson could face five years in federal prison.