Armstrong was born in 1973 and served in the United States Navy aboard the aircraft carrier Nimitz, which took him to ports in Asia, the Mediterranean and the Middle East. He lived in Dearborn, Michigan, married, with a child.
Between 1992 and 1999 he strangled women in the Detroit area, most of them working as prostitutes, and left bodies in the Rouge River and in derelict ground. He was arrested on April 12, 2000 after reporting that he had found a body himself, which drew attention to him.
In interview he described killings in Hong Kong, Thailand, Singapore, Israel, Virginia and Washington state, putting his own total as high as thirty. Naval investigators and police forces in several countries examined what he had said. Some of it corresponded to unsolved deaths and none of it produced a charge; much of it could not be checked at all, the deaths of women in those circumstances in those ports often not having been recorded as anything.
He was convicted of five murders in Michigan and sentenced on April 3, 2001 to life imprisonment without parole.
The range of five to eighteen sits between the convictions and the claims. The entry keeps the convictions as the count and records the rest as what he said, because that is all it is: no foreign jurisdiction has ever charged him with anything.
The case did prompt a question in the United States about whether a serving sailor's movements between ports were tracked in any way that would allow a pattern to be seen. They were not.