SEATTLE - Federal agents have arrested a mystery man who has used so many different identities over so many years they don't know who he really is.

"This is a really unusual situation," said FBI spokesman Robbie Burroughs. "To have a person, and we have no idea who he is."

Sometimes he calls himself William Everett Gee. Other times he's Robert Allan Lowe, or Robert Allan Loew, or any one of many other names.

The FBI says he is actually none of the above.

"I mean we believe now that this has been going on for over 20 years," Burroughs said.

When he was arrested, investigators found several IDs on him. They all had his picture but with dozens of different names.

On some of the IDs, he had lots of hair, on others a little less and sometimes he was bald. He wore glasses or no glasses, he looked younger or older. Investigators say he even tried to burn off his fingerprints using chemicals.

"He's not helping us," Burroughs said. "He's not telling us why he did it. He's not telling us who he is."

In the meantime, federal agents are referring to him simply as John Doe.

Burroughs said they have no evidence that the mystery man is stealing money or defrauding anyone. But he is using the identities of many people who died years ago - using their Social Security numbers, birthdates and other information.

His last known address was in a commercial office building in Queen Anne. People working inside said they saw him living in a small office without a bed and no kitchen.

The mailbox outside had yet another name on it.

The mystery man is being held at the Federal Detention Center in SeaTac. He faces seven criminal charges, including fraud and aggravated identity theft. And agents want to know whether he used his multiple identities to commit other crimes as well.