On February 14, 2017, the bodies of Abigail Williams and Liberty German were discovered near the Monon High Bridge Trail, which is part of the Delphi Historic Trails in Delphi, Indiana, United States, after the young girls had disappeared from the same trail the previous day. At 1:35 p.m. on February 13, 2017, 13-year-old Abigail J. "Abby" Williams and 14-year-old Liberty Rose Lynn "Libby" German were dropped off by German's older sister, Kelsi German, at a trail-head on County Road 300 North, west of the Hoosier Heartland Highway. The girls were hiking on the Monon High Bridge over Deer Creek, among woodland in remote Deer Creek Township, when they were last seen. They were reported missing at 5:30 p.m. when they failed to meet family at the end of the trail. The murders have received significant media coverage because a photo and audio recording of an individual believed to be the girls' killer was found on German's smartphone. On February 22, law enforcement released an audio recording where the voice of the assailant, though in some degree muffled, is heard to say, "Down the hill."
On July 17, 2017, officers distributed a composite sketch of someone who, at that time in the investigation, was sought as a person of prime interest in the murders. On April 19, 2019, it was further explained that the previously-released sketch, showing an older man with goatee and cap, depicted a different person of secondary interest. By contrast, the clean-shaven individual of the newly revised composite is the prime suspect. Police say this person may range from his 20s to his 30s, but caution that his "youthful appearance" could make him look younger than his true age.
Daniel J. Nations, a registered sex offender from Indiana, was arrested in Woodland Park, Colorado in September 2017 and charged with threatening strangers on a Monument trail with a hatchet. The expired Indiana plates on the car Nations was driving was noticed by police. Fanning public speculation still further, it was reported that a bicyclist had been fatally shot on the same trail at around the time that Nations was purportedly terrifying passersby. On January 5, 2018, Nations was sentenced to three years of probation for threatening members of the public in Colorado; however, he was not released since he had an active warrant out on him back in Indiana. On January 24, Nations was finally transferred to Indiana officials' custody on an unrelated charge, failure to register as a sex offender. In early February 2018, authorities said that Nations was no longer considered an active person of interest in the Delphi murders.
Thomas Bruce, who formerly worked as a pastor, is charged with fatally shooting one woman and sexually assaulting two others, after having ordered them at gunpoint into the back room of a suburban St. Louis shop for religious supplies. Committed in broad daylight on November 19, 2018, these crimes put Bruce in the spotlight of the press. Some noted his being of similar stature (5-foot-7 to 5-foot-9 inches) to the then-current suspect description in the Delphi slayings; also, his wearing a flat cap and navy-blue jacket during this attack, not unlike the suspect in the Delphi case. Indiana State Police did look into his possible connection in November. On December 4, Bruce was charged with no fewer than 17 felony counts related to the St. Louis case and could receive the death penalty.
Charles Eldridge was arrested on January 8, 2019 in Union City, Indiana, on charges of child molestation and child solicitation. Police in Randolph County alerted the FBI to a potential link between Eldridge and the Delphi murders, on account of his strong resemblance to the original (Delphi) suspect sketch.
On July 23, 2019, after receiving a tip, authorities announced that Paul Etter was being considered a suspect in the murders. Etter was wanted for the kidnapping and rape of a 26-year-old woman on June 22 in Tippecanoe County. Five days later, Etter was surrounded by police, and after a five hour stand-off, he committed suicide.