A $14,000 debt in a drug deal may have led to the bizarre strangulation death of a 31-year-old Colorado man whose body was found tied to a mobile walker on a sidewalk near Union Square, according to court documents filed Tuesday in San Francisco.

The victim, Andrew Emmett, was found dead on Feb. 7, one day before a Petaluma couple and their teenage son were arrested in connection with the slaying.

Court documents describe an eerie chain of events that include the strangled and beaten body of the victim being tied by his shoelaces to the mobile walker, wheeled by his family of alleged killers from his fifth floor hotel room into an elevator and then through the hotel lobby and onto the 500 block of Post Street, at which point the three suspects abandoned Emmett’s body and fled in a car.

Arrested were three members of the Hardee family — Christopher Hardee, 47; his wife, Nicole, 40; and their son, Kayleb, 19. They appeared in court on Tuesday in San Francisco, where they were ordered to be held without bail and to return to court on Thursday.

All were charged with murder with special circumstances, making them eligible for the death penalty if convicted.

According to Assistant District Attorney J. Michael Swart, Emmett, a visitor from Breckenridge, Colo., checked into room 504 of the Dakota Hotel on Feb. 7 and, about an hour later, met the Hardees in the hotel lobby and returned to his room accompanied by Christopher and Kayleb Hardee.

About three hours later, Nicole Hardee received a phone call, brought a mobile walker to the lobby and gave it to her son. A short time later, the two men appeared in the lobby, with Christopher Hardee wheeling the walker with the victim “tied into the device via his shoelaces.”

“Christopher Hardee then pushed the mobile walker for a few yards on the sidewalk and abandoned the walker, fleeing with Kayleb Hardee to a car driven by Nicole Hardee,” according to a statement of facts filed by the district attorney’s office.

Further investigation led police to the Hardees’ home in Petaluma. In their car, police found Emmett’s bloody clothing. Inside their home, police found “indication of marijuana sales” and documents inside a safe that showed Emmett owed $14,000. A search of a Petaluma motel room led to the seizure of 18 pounds of marijuana, one shotgun and one handgun.

Emmett was killed “as a result of ligature strangulation as well as blunt force trauma,” according to court documents.

Nicole Hardee told police she had come to San Francisco to have lunch with Emmett and go shopping at Macy’s, the documents said.

Attempts to reach attorneys for the suspects were unsuccessful.

Steve Rubenstein is a San Francisco Chronicle staff writer. Email: srubenstein@sfchronicle.com Twitter: @SteveRubeSF