Prosecutors say the man charged in the Gilgo Beach serial killings on Long Island, New York, kept a document he used to “blueprint” his crimes. Prosecutors say in a court filing Thursday that investigators discovered a “planning document” on the hard drive found in Rex Heuermann’s basement that they believe he used to “methodically blueprint” his killings. They say the document includes Heuermann’s concerns about leaving behind forensic evidence, guidance for cleaning and washing bodies, and notes on how to improve “next time,” according to the bail application. Heuermann appeared at a hearing Thursday and pleaded not guilty to charges alleging that he killed Jessica Taylor and Sandra Costilla. He was previously charged in the killings of four other women.