A Derry woman and her 2-year-old son were struck by a train and killed last night as she struggled to push his stroller across the tracks in the Westmoreland County borough.

Sheila Singer, 37, her son, John Smart, and her two young daughters had just finished grocery shopping on East First Avenue about 5 p.m., officials said, and were taking a shortcut across a double set of railroad tracks to get to their home.

They had crossed one set of tracks and had begun to cross the second set when Ms. Singer and the stroller were struck by the westbound Norfolk Southern train, said Dan Stevens, a spokesman for the Westmoreland County Department of Public Safety.

Ms. Singer's other children managed to dart across the tracks safely and saw the accident from the other side.

The impact threw Ms. Singer about 50 feet and off the tracks, while John was swept under the train, said deputy county coroner Chris O'Leath.

The surviving children were taken to a hospital, though they appeared to be physically unharmed, Mr. Stevens said.

"Psychologically, they are traumatized," Mr. Stevens said.

Derry police Chief Randy Glick, who was on routine patrol in the nearby shopping plaza, saw the train approaching and repeatedly motioned and yelled for Ms. Singer to move from the tracks.

The chief through Mr. Stevens declined to comment.

The train blew its horn as it routinely does and is required to do as it passes through Derry, Mr. Stevens said. The speed limit in that area is 60 mph, he said, and there was no indication that the train was speeding.

A Norfolk Southern spokesman said the company is cooperating with police in their investigation, but declined further comment.

"Railroad tracks are not something to play around with," Mr. Stevens said. "You're risking your life when you do."

The stretch of tracks is a known trouble spot and was the site of another fatal accident this summer. In July, Douglas Albright, 15, of South Greensburg, was struck by a Norfolk Southern train while crossing tracks in the 100 block of East First Avenue.

After his death, officials spray-painted "no trespassing" on signs on both sides of the track, but "People look at them and they laugh," Mayor Susan E. Bortz said. "They ignore them.

"I think people depend on their senses, that they might hear a rumble, but it just doesn't happen."

Last night's incident, she said, underscores the need for a pedestrian bridge over the tracks, something neighbors who gathered at the scene said they've wanted for a long time.

"We've been hounding legislators and trying our best to get an elevated crossway," Ms. Bortz said.

"Enough is enough," said resident Debbie Rager. "There's been too many, too close. Get a walking bridge built."

There is a bridge over the tracks about 50 yards from the site of the accident. Ms. Singer should have crossed there, Mr. Stevens said.

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