(NewsNation) — A former NYPD detective said it’s likely that the suspected Gilgo Beach murderer “was trying to perfect the way to avoid detection” after new evidence showed he likely blueprinted his crimes.

“Who would expect something like this? But it looks like each time he (Rex Heuermann) committed a murder, he was trying to perfect the way to avoid detection,” said David Sarni.

Rex Heuermann, the man already suspected in the deaths of four women found near Long Island’s Gilgo Beach, was charged Thursday in the murders of two more women during his latest court appearance.

According to a bail application released Thursday morning by Suffolk County District Attorney Ray Tierney, Heuermann faces additional second-degree murder charges for the deaths of Jessica Taylor and Sandra Costilla.

Sarni told NewsNation’s Elizabeth Vargas that the latest evidence against Heuermann is particularly damning.

“This really damaging evidence puts him with both of these bodies,” said Sarni. “And now a blueprint of what he did with those bodies. The tenacity and the work done by the investigators now and in the past.”

Police have searched Heuermann’s home twice, and one piece of evidence they said they found in his basement was a Microsoft Word document named “HK2002-04.” Though it had been deleted, forensics experts were able to recover it. Included in the documents was a “checklist of supplies” including ropes, saws and surgical drapes.