Claiming to have murdered as many as 80 women, Gary Ridgway — known as the Green River Killer for the Seattle, Washington, location where many of his victims were discovered — was America’s deadliest convicted serial killer when, in 2003, he pleaded guilty to 48 counts of murder.

Over 20 years, Ridgway methodically raped and strangled scores of women, many of them prostitutes or runaways, dumping their bodies across a wide area of King County to confuse authorities. Investigators believe that, throughout his murderous spree, the seemingly mild-mannered Ridgway never spoke to anyone of his killings or kept trophies of the grisly crimes. All the while, he maintained his longtime job as a truck painter at the Kenworth Truck plant in Renton and married for the third time.

Watch the special three-night event, Invisible Monsters: Serial Killers in America, beginning Sunday, August 15 at 9/8c on A&E.

July 15, 1982: The body of Ridgway’s first victim is discovered

In July 1982, children found the strangled body of Wendy Caulfield, 16, floating in Seattle’s Green River. Over the following weeks four more bodies were discovered in or along its banks — all women, all strangled. On August 15, three more bodies were found and detective David Reichert was one of the first authorities to arrive at the scene. Marci Chapman, 31, was found in the shallow water alongside the naked body of 17-year-old Cynthia Hinds, and nearby in the undergrowth lay the body of Opal Mills, 16, blue trousers knotted around her neck, breasts exposed, bruises apparent on her arms and legs.

August 16, 1982: A police task force is set up

After the King County Sheriff’s Office set up the Green River Task Force to investigate the killings, the body count rose, as more victims were discovered along the river and in the area around the Seattle-Tacoma International Airport.

Over the next two years, the Green River Killer sexually assaulted and murdered more than 40 other women. “Every time you found a body, it was like being hit on the head with a baseball bat,” Reichert told Time magazine.

April 30, 1983: Ridgway first becomes a suspect

In the spring of 1983, prostitute Marie Malvar, 18, was last seen by her boyfriend getting into a paint-patched pickup with a dark-haired man about 30 to 40 years old. Four days later, police questioned Ridgway at his home about his knowledge of Malvar, whom he denied knowing. In November, police once again spoke with Ridgway about the murders, but he denied any knowledge of the victims, and authorities lacked evidence to connect him to any of the crimes.

In 2003, Ridgway told investigators he stood against a fence during his original 1983 questioning to conceal scratches Malvar had left on his arm while trying to escape. Ridgway said he then burned the scratches with battery acid to disguise them once the detectives had left.

May 1984: Ridgway passes a polygraph test

Already a person of interest due to his known association with area prostitutes, Ridgway contacted police with the supposed intention of assistance. He then passed a polygraph test in which he denied killing any women.

1986: The police talk with Ted Bundy

With few reliable leads in the Green River Killer case, authorities were desperate for any information to further the investigation. Having read about the ongoing case in the press, convicted serial killer Ted Bundy wrote to Reichert offering his help in the case. Reichert flew to Florida where Bundy was being held on death row. During discussions, Bundy reportedly advised authorities that the killer may be revisiting his victim’s corpses and performing sexual acts on them, a hypothesis Ridgway later confirmed.

READ MORE: How Ted Bundy Helped Catch the Green River Killer

1987: Ridgway provides a DNA sample that would eventually be his downfall

Because Ridgway wass the last person allegedly seen with two of the victims, police eventually searched his home and vehicles in 1987 in connection with the murders. It was at that time Ridgway finally provided police with a saliva sample that would later tie him to the crimes. But due to insufficient DNA testing at the time, Ridgway remained a free man for more than a decade.

March 2001: DNA testing expands and connects Ridgway to three murders

With new techniques in forensic testing at their disposal, investigators re-examined evidence from across the years the killer had been active. “It was a last-ditch effort,” Beverly Himick, a Washington State Patrol Crime Laboratory forensic scientist, told The New York Times. “We didn’t have a lot to work with, but we went through a lot of evidence again. We rinsed all the fingernails to look for trace evidence and swabbed the ligatures for cellular material. With one girl, we were able to find a few sperm clinging to her pubic hair.”

New DNA profiles from three victims were compared with Ridgway’s, thanks to the saliva sample he had provided in 1987. It was a match in all three cases.

November 30, 2001: Police announce the arrest of the Green River Killer

Nearly two decades after the first murder, King County Sheriff Reichert announced that Ridgway, 52, was arrested in connection with four of the Green River Killer’s early victims: Marcia Chapman, Opal Mills, Cynthia Hinds and Carol Ann Christensen — whose body was recovered in 1983.

November 5, 2003: Ridgway pleads guilty

In a plea bargain that would spare him the death penalty in return for his confession and information regarding the details of the murders and locations of the bodies, Ridgway entered a guilty plea to 48 charges of aggravated first-degree murder.

“I killed so many women I have a hard time keeping them straight,” Ridgway said in a statement, admitting he killed most of his victims in his house or truck before disposing of the bodies, adding that in most cases he did not even know his victim’s names. “Most of the time I killed them the first time I met them, and I do not have a good memory for their faces.”

Explaining why he chose women he thought to be prostitutes, Ridgway said they “were easy to pick up without being noticed. I knew they would not be reported missing right away and might never be reported missing. I picked prostitutes because I thought I could kill as many of them as I wanted without getting caught.”

December 18, 2003: Ridgway is sentenced

For his crimes, a King County Superior Court Judge sentenced Ridgway to 48 life sentences, to be served consecutively, with no possibility of parole.