Jul 11, 2012 7:12 PM

A Roman Catholic nun was struck and killed by a hit-and-run driver on Monday night in Water Mill, and police have identified the suspected driver and are actively trying to track him down.

The nun, Sister Jacqueline Walsh, 59, was walking along the side of Rose Hill Road, a short distance from a Sisters of Mercy retreat house, where she had come for a religious retreat, at about 8:30 p.m., when she was struck by a 2009 Volkswagen Touareg, Southampton Town Police said. The driver—police have reportedly identified him but have not released his name—ditched the Volkswagen about a half mile from the accident scene, police said.

As of Wednesday morning, police had yet to make an arrest, but the driver has been identified as a local resident.

“We know who the driver of the car is, and there are police officers right now on the street trying to locate him,” Suffolk County District Attorney Thomas J. Spota said during a press conference Tuesday afternoon on an unrelated topic at his Hauppauge office. “He lives in the community where the incident occurred. We’re looking for the individual, but we know who he is.”

Police did not return several calls seeking comment on the suspect or how they identified him.

Known among her colleagues simply as “Sister Jackie,” Ms. Walsh had been walking along the normally quiet Rose Hill Road, a dead-end street without a sidewalk on which the retreat, Mercy Villa, is located. The posted speed limit there is 30 mph. At about 8:30 p.m., police started receiving calls of a female lying on the ground and describing her as “bleeding and unresponsive.”

Ms. Walsh was a member of the Sisters of Mercy of the Americas, a Catholic order whose mission involves helping the sick, poor and uneducated. She was pronounced dead shortly after police arrived. Her body was found on the east side of the road at the end of a driveway of a property neighboring the retreat, officers said.

The unoccupied Volkswagen—with front-end damage—was found about a half mile from where Ms. Walsh’s body was found, detectives said. Based on a description they said was provided by people who arrived at the scene shortly after the accident, and who apparently saw a man at the scene before he disappeared, the motorist was described as a “white Hispanic” male, about 5 feet 7 inches tall, in his 20s or 30s, with short spiked hair and wearing dark shorts and a white shirt.

“We are dedicating significant investigative resources to this tragic event,” said Town Police Chief William Wilson Jr. “We will not rest until all possible evidence and information is followed and leads to the apprehension of the individual responsible for the sister’s death.”

Police have not answered several key questions about the fatal accident, including who the registered owner of the car is, whether the suspect is the car’s owner or whether the vehicle had been reported stolen.

Ms. Walsh joined the Sisters of Mercy in 1981. A Brooklyn native, she lived in a Syosset convent and had taken the Sisters of Mercy vows of poverty, obedience, chastity and service. She had been ministering as a pastoral associate at St. Edward Confessor Church in Syosset since 2003. Prior to that, from 1997 to 2003, she was the campus minister at Our Lady of Mercy Academy, a Catholic girls high school in Syosset. From 1994 to 1997, she taught theology at the same school, according to Debbi Della Porta, the director of communications for the Mid-Atlantic Community of the Sisters of Mercy.

The type of retreat she was on is typically used for a time of solitude, when sisters and laypeople contemplate their lives and faith, Ms. Della Porta said.

“Jackie was well-loved, a woman of faith, warmth and humor who touched the lives of many with her joy and concern for others,” Ms. Della Porta wrote in an emailed statement she attributed to Sister Patricia Vetrano, the president of the Mid-Atlantic Community. Ms. Della Porta said the Sisters of Mercy were heartbroken and devastated by the death of their fellow sister.

A car was parked at each entrance to the horseshoe driveway in front of Mercy Villa on Tuesday afternoon, blocking entry to the retreat.

Several nuns spotted coming and going declined to comment on the incident or Ms. Walsh, instead explaining that they had been instructed to refer all questions to Ms. Della Porta.

One nun, who did not give her name, did offer a few words about her fallen sister. “Jackie was a great person. I’ll say that,” she said, adding that Ms. Walsh had gone out alone and was headed back to the retreat at the time she was killed. She declined further comment, climbing into her car parked in front of the retreat.