A car inadvertently left in gear in the driveway of a Laurel-area home Friday backed over a mother and her two young children, killing a 3-month-old girl and injuring the other family members, authorities said.

The incident occurred about 9 a.m. in the 8300 block of Montpelier Drive, and appears to be a tragic accident, said Cpl. Mike Rodriguez, a spokesman for the Prince George’s County Police Department.

The children’s mother pulled into the driveway of the home to drop off her children, but she got out of her car without putting it in park, Rodriguez said. As the mother gathered her infant daughter into her arms, she noticed the car was rolling backward toward her 3-year-old son, who was screaming behind it, Rodriguez said.

With her daughter still in her arms, the mother, 28, rushed to the aid of her son, Rodriguez said. Cpl. Henry Tippett, another police spokesman, said the mother got hit by the open driver’s side door and fell underneath the car, still holding the baby.

The vehicle rolled over her and her two children, fatally injuring the baby girl, Tippett said. The others, he said, were taken to a hospital and are expected to survive.

Police identified the baby as Sarah Aryeequaye. They declined to release the name of the mother and her son, who live in Laurel, Rodriguez said.

Melvin Smith, 41, a neighbor, said he heard screaming and rushed outside to see the mother, covered in blood, sitting and cradling her daughter in her arms. Smith said he told another neighbor to call 911, and he started performing CPR on the baby.

“She was just yelling out, ‘God please help my baby! God please help my baby!’ ” Smith said of the mother. “It’s devastating because I did everything I could.”

Pam Harrison, 42, another neighbor, said she called 911, then helped Smith perform CPR. The mother never let her daughter out of her arms, and it was clear that their efforts were fruitless, Harrison said.

“She just kept praying to God, don’t take her baby, don’t take her baby,” Harrison said. “That was horrific.”

Harrison said the 3-year-old boy was walking around while neighbors tended to the baby. The boy did not appear to be seriously injured, she said.

The driveway of the Laurel home is only slightly inclined, but when a police collision-reconstruction team tested it later, the car picked up significant speed as it rolled.

Tippett said the woman was dropping off her children at a babysitter’s house.

Rodriguez said police accident experts will prepare a report and work with the state’s attorney’s office to determine if charges were warranted. Those types of reports typically take months to complete.

Efforts to reach family members were unsuccessful Friday. No one answered the door at the home where the crash occurred, and no one returned a written message left there.