Shocking new details in Watts family massacre. Cops believe missing Iowa college student Mollie Tibbetts was killed while jogging.

Crime & Justice with Ashleigh Banfield

The weekslong search for Mollie Tibbetts, a 20-year-old Iowa student who disappeared while jogging, came to a grisly end Tuesday when a man guided investigators to a body in a cornfield. While authorities have yet to confirm the body is Tibbetts, they arrested Cristhian Bahena Rivera, 24, on first-degree murder charges. The discovery dashed the hopes of family and friends who had scoured Poweshiek and nearby counties as rewards grew to nearly $400,000. Tibbetts, officials said, is believed to have been abducted on July 18 as she went out for an evening jog. Rivera, who's an undocumented immigrant, told them Monday that he saw and pursued her, getting out of his car and running beside Tibbetts. She warned him she would call police, officials told reporters Tuesday. The suspect, who said he blacked out at some point, led authorities to the field Tuesday morning, they said. A body, dressed in Tibbetts' clothing, was covered in corn leaves. A murder suspect told police in Colorado he strangled his pregnant wife in a rage after he saw her on a baby monitor strangling the couple's 3-year-old daughter, Celeste, according to court documents. Chris Watts said the couple's other daughter, Bella, 4, was already "sprawled out" on the bed and blue in the couple's bedroom, according to an arrest affidavit from Frederick police. Watts confessed to burying his wife, Shanann Watts, 34, near two oil tanks and dumping his daughters' bodies in the tanks, according to the affidavit. But prosecutors paint a different picture of the killing. Watts was charged Monday with three counts of first-degree murder in the deaths of his wife and young daughters. Two additional first-degree murder charges accuse him of causing the death of a child younger than 12. Watts, who was arrested last week, is being held without bond. via Knit