A westbound Norfolk Southern train roared through Derry Borough yesterday, along the stretch of tracks where a mother and her 2-year-old son were killed the night before.

The final freight car passed, revealing a heart-shaped wreath tied to a fence and an unsigned note: "In loving memory of Sheila and John-John."

"Sheila" was 37-year-old Sheila Singer, the Westmoreland County coroner's office said, a mother of five who had moved to the small community from Connellsville this summer to reunite with her fiance, Elmer Smart, those close to her said.

She brought with her the couple's three children -- 4-year-old Mindy, 13-month-old Elisha, and a 2-year-old son, John.

They lived in a white-brick apartment on East Second Street, next to the railroad tracks. Neighbors said she often ran errands at the shops on the other side of the tracks.

On Friday night, police said, Ms. Singer and her children, returning home from a market, took a shortcut across the double set of tracks, a straightaway not authorized for crossing.

Ms. Singer helped Mindy across first, then returned for Elisha, who was in a carrier, and John, in a stroller. As she took them across, the coroner's office said, John's stroller got struck in the track. Derry police Chief Randy Glick, on patrol in the area, saw the train approaching and yelled to Ms. Singer as she moved Elisha in the carrier off the track and returned for John in the stroller.

She continued to cross, and she and her son were killed in plain view of the two little girls. Some residents who visited the accident site yesterday wondered why Ms. Singer did not heed the chief's calls.

Investigators, who ruled the deaths accidental, have said they might never know why. But Heather Singer, who is married to Sheila Singer's ex-husband, Norman, offered a possible explanation yesterday, recalling Sheila as a devoted mother with a strong Christian faith.

While others might flee in times of sudden stress, Sheila "would freeze," Heather Singer said.

"It was just part of who she was," she said. "I cannot imagine her doing this on purpose."

She described the accident as a tragic end to a challenging life that appeared to be on the rebound.

Ms. Singer's older daughters, Samantha, 11, and Ashlie, 13, live in Champion with Heather and their father and had not yet been told yesterday afternoon of their mother's death.

"It's really just a shock," Heather Singer said. "I know her kids are really going to miss her."

For years, Sheila Singer raised Ashlie and Samantha as a single mother. With Mr. Smart, she had Mindy, John and Elisha -- named after Ashlie, with the letters re-arranged. Mr. Smart and Ms. Singer lived in Greensburg for a time, Heather Singer said, but their troubled relationship prompted Ms. Singer to move to Connellsville to be closer to her mother, who had assisted her in the past.

But Ms. Singer's mother became ill, Heather Singer said, and could not help her as much. So she opted to move to Derry and reconcile with Mr. Smart.

"She was very distraught," Heather Singer said. "She told me she thought she didn't have anywhere else to go. She flat out said, 'There's no one else to take care of me.' "

Ashlie and Samantha moved to Champion when Ms. Singer moved to Derry in July, Heather Singer said. Their mother visited them at least twice a week, sharing dinner, doing craft projects and hanging out for hours.

"She was a mom," Heather Singer said. "She didn't work. She was home all the time with the kids."

Derry was an adjustment. Neighbor Dawn Dupuis said Ms. Singer was "a very quiet person, and the children were just so sweet."

Another neighbor, Mary King, said it appeared that Ms. Singer was warming up to Derry. Sometimes, she offered to babysit Ms. King's grandchildren, and Ms. King would return the favor. They would spend time on the porch while the children played nearby.

"She'd do anything for you," she said.

Mr. Smart, she added, was excited to have her and the children back in his life.

"Elmer was always bragging about them," said another neighbor, June Sloan.

Heather Singer, too, said Ms. Singer was progressing, despite bouts of sadness due to the rough year. In July, she said, Ms. Singer sought inpatient mental health treatment, which continued later with doctor's visits.

"It seemed to be really helping her," Heather Singer said. "She was really trying to get everything together for herself."

Visitation for Sheila Singer and her son is from 5 p.m. to 8 p.m. tomorrow at the City Church, 206 N. Pittsburgh St. in Connellsville, where Ms. Singer was a longtime member. The funeral is at 11 a.m. Tuesday at the church.

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