Lubbock District Attorney Matt Powell said Patterson died of natural causes.
Patterson was convicted of killing Kay Harrelson in September 2011. He is also accused of killing Peggy Merriman. The three worked together at the Lubbock State School.
Powell said Patterson died at the Clements Unit in Amarillo, where he had been housed for about a month.
Stay with EverythingLubbock.com, KAMC and KLBK for more on this story.