A 57-year-old convicted rapist has pleaded guilty to killing a young NASA intern and the rapes of two University of Maryland students during the early 1990s.

Thomas Lee Posey, a longtime Maryland prisoner, has pleaded to first-degree murder in the June 1990 rape and strangulation of 22-year-old Margaret Perkins, an intern at the Goddard Space Flight Center in Greenbelt. Posey last week also admitted to raping two different college students in May and September of that same year.