Susan Murphy-Milano...

The deaths happened Tuesday in the midst of a legal fight 28-year-old Magdalene Kamysz was waging over the daughter police suspect she killed.

Sydney Kamysz was found dead in her Crystal Lake home about 6 p.m. after a McHenry County deputy coroner went there to notify relatives that Magdalene Kamysz had been killed by a train about four hours earlier.

One focus of the inquiry is an ongoing legal battle Kamysz was waging with Sydney's father over custody and visitation issues.

"It has been a somewhat heated and contested situation," Nygren said.

Sydney's father, 29-year-old Alan Burton of Walworth, Wis., filed a civil suit in February seeking to formalize his visitation rights with the girl, which his attorney said had been disrupted earlier.

While Burton and Magdalene Kamysz had never married, Burton regularly visited his daughter and helped support her, said his attorney, Margi Worth.

Burton was seeking joint custody of the child but wasn't attempting to remove her from Kamysz's care, Worth said.

"He had a relationship with his daughter and was seeking to continue that relationship, which had been denied to him," Worth said.

The case was still pending after three sessions with a mediator failed to produce an agreement.

Kamysz's attorney said he had seen no indications that she was upset about the legal case.

"I'm at a loss. I found her to be a loving mother," said attorney Wesley Pribla. "I found her to be a concerned parent."

Sydney, who would have started the second grade Wednesday, was found lying in a bed in the room she shared with her mother. The door to the room was locked, and there were no signs of forced entry to the home, which she and Kamysz shared with Kamysz's parents.

Preliminary autopsy results indicated the girl had been suffocated, Nygren said, though toxicology and other forensic tests were still pending.

A few hours before her little boy and girl died in a fire she set, Nimisha Tiwari brought them to a store and bought the playthings later found near their bodies: a Dora the Explorer doll and a Thomas the Tank Engine toy.

Shortly before that, Tiwari took the children with her in the family minivan to buy the gasoline she used to ignite the fatal blaze.

That's the picture painted by police before Tiwari, 32, set her house ablaze Saturday, killing herself, her 18-month-old daughter, Anaya, and her 4-year-old son, Vakadham. All three were found on the same bed in the master bedroom of their locked Naperville home.

Police -- who used footage from security cameras to piece together Tiwari's movements before the fire -- are trying to determine a motive "for such a horrific incident," Naperville Police Chief David Dial said at a news conference Monday.

"It is tragic. It is senseless," Dial said. "I can't explain why."

While court records suggest marital strife, "There is nothing to indicate that this is anything more than a double murder-suicide investigation," Dial said.

Tiwari called her husband, Anand Tiwari, abusive and controlling, according to court documents. He said he feared her increasingly erratic behavior -- which he blamed on multiple sclerosis -- might endanger their son and daughter, the records show.

Authorities believe Tiwari gathered her children Saturday afternoon in the second-floor master bedroom of their home, in the 1900 block of Nutmeg Lane, part of Naperville's Cinnamon Creek subdivision. She poured gasoline on the hallway floor outside the room, and doused the bedroom floor as well. She may have splashed her own body with gas before igniting the blaze, police said. A lighter was found on her body. The front door was locked.