(NewsNation) — Suffolk County District Attorney Ray Tierney continues to “expand the investigation” into suspected serial killer Rex Heuermann.

“There’s nothing off limits,” Ray said on “CUOMO.” “We’re going to continue to follow the evidence to its conclusion, and we’ll let the chips fall where they may.”

Heuermann, already suspected in the deaths of four women found near Long Island’s Gilgo Beach, was charged in the murders of two more women Thursday 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.

Taylor, 20, went missing in 2003 while working as an escort in New York City. Some of her remains were discovered in Manorville that year, and more were found by the side of Ocean Parkway. The body of 28-year-old Costilla was discovered in 1993.

Since 2010, police have been probing the deaths of at least 10 people, most of whom are sex workers, whose remains were discovered along an isolated highway not far from Gilgo Beach. Victims had gone missing over a span of at least 14 years. 

Ray said that as authorities expanded the investigation, “different facts came to light.”

“Taking that information, we followed the evidence and we took the necessary investigative steps,” Ray said Thursday.

Heuermann, an architect who lived across a bay from where the bodies were found, was arrested last July in connection to the killings of Megan Waterman, Melissa Barthelemy, Amber Lynn Costello and Maureen Brainard-Barnes.

At Thursday’s hearing, Heuermann pleaded not guilty to killing Taylor and Costilla and was ordered held without bail. Michael Brown, Heuermann’s attorney, told reporters later that Heuermann is “horrified by the new charges,” and “obviously in a bad place” regarding them.

NewsNation’s Laura Ingle contributed to this report.