A newly filed Fairfax County criminal complaint alleges the man accused of fatally stabbing a woman on Difficult Run Trail told a witness beforehand that he planned to kill her.

Alexis Antonio Cedillos-Campos, 19, is charged with second-degree murder in the Monday, Aug. 17 stabbing death of Carmen Lizet Puch, 42, of Reston, along the trail in Great Falls Park off Georgetown Pike. The two worked together at a restaurant in Herndon and had been in an intimate relationship, according to the Fairfax County Police Department (FCPD).

The complaint, reported by WTOP, describes a witness who told police Cedillos-Campos left work early that Sunday after Puch sent screenshots of their affair to his girlfriend. He was upset and said he was going to kill Puch, the witness told police. Cedillos-Campos then left the restaurant wearing black latex gloves and carrying a kitchen knife and a water bottle, WTOP reported.

Around 4 a.m., Cedillos-Campos called the witness to say he had done it. He hung up immediately.

Officers with the FCPD's McLean District Station were dispatched to the 8800 block of Georgetown Pike at 6:43 a.m. on Aug. 17 after a runner called 911 to report finding a woman unconscious outside her car in the parking lot, FFXnow reported. Puch had suffered multiple stab wounds. She was pronounced dead at the scene.

A water bottle found near Puch's body smelled of gasoline, as did Puch herself, according to police. Investigators determined Cedillos-Campos had filled the bottle with gasoline siphoned from his motorcycle and attempted unsuccessfully to set her body on fire. Detectives also found a cellphone case near the body but no phone; call records showed Puch's last communication was with a number belonging to Cedillos-Campos.

At a Wednesday, Aug. 19 press conference, Fairfax County Police Chief Kevin Davis called restaurant surveillance video showing Cedillos-Campos arming himself "eerie" and said the case "certainly sounds premeditated to me."

Cedillos-Campos was arrested that same day in Prince George's County, Maryland, after a brief chase involving the FCPD's Fugitive Tracking and Apprehension Team, Prince George's County police and the U.S. Marshals Service, according to an FCPD news release. Police said he offered a full confession.

He is being held at the Fairfax County Adult Detention Center without bond. U.S. Immigration and Customs Enforcement lodged an immigration detainer the same day, according to Patch. The Department of Homeland Security said Cedillos-Campos, a native of El Salvador, entered the country through Texas in April 2024 and was released after being taken into custody by U.S. Customs and Border Protection.

Davis said at the press conference that a first-degree or aggravated murder charge remained a possibility depending on what prosecutors with the Fairfax County Commonwealth's Attorney's Office decide. The charge is an accusation, and Cedillos-Campos is presumed innocent unless proven guilty.

A preliminary hearing is scheduled for Nov. 30.