Danno and Martinez-Hernandez are charged with first-degree murder. They are being held without bond.
Officials said the women were strangled in the Dannos' Southwest Side home, and their bodies were then transferred to the car, driven to Cap Sauers Forest Preserve in Palos Park and set on fire Saturday night.
"They went out and got one of the garbage cans in the City of Chicago, one of the big black garbage cans. They wheeled it inside. They put Mary Ann in the garbage can, they wheeled her out [to the] back of the house and put her in the back of her vehicle, which is a PT Cruiser. They then went inside and took the mother-in-law, Theresa, and put a blanket over her and took her to the vehicle as well," Cook County Sheriff Tom Dart said. "They took the vehicle there, they doused it with gas that they got earlier in the day they then lit it on fire. Robert had sustained burns on his arms."
Surveillance cameras at gas stations and traffic lights were used to track down the suspects, Dart said.
Money may have been the motive, officials said. Urban had $500,000 in the bank and two properties in Lake Geneva, Wisconsin. Sheriff Dart said Urban-Danno wanted a divorce. Neighbors said Danno and Martinez-Hernandez, a homeless man who Danno had taken in last November, were living together in the basement of the Danno home.
Authorties said they had been called to the Danno home for domestic disputes in the past.
Neighbor Teresa Taplin said Urban-Danno was a kind neighbor who would buy Girl Scout cookies and volunteer at church.
"Mary Ann was an extremely nice lady and she'll be missed," Tapling said.
Both men made videotape confessions, police said.