Authorities are conducting an international manhunt for the driver police believe killed a nun in Water Mill in a hit-and-run crash in July, according to a law enforcement source with knowledge of the case.

Federal agents abroad are heading up the search for Southampton laborer Carlos Armando Ixpec-Chitay, 30, who is believed to have fled the country -- possibly to his native Guatemala -- after the crash that killed Sister Jacqueline Walsh, 59, of Syosset on July 9, the source said.

U.S. marshals, working with Southampton Town police, nearly captured Ixpec-Chitay at least twice. They missed him by only a few minutes after being tipped off to the undocumented immigrant's whereabouts after he left New York, the source said.

"We hope they catch him, wherever he is, or that he simply does the right thing and turns himself in," said Walsh's longtime friend, Linda Dwyer of Syosset. "We will forgive him, just as Sister Jackie would have forgiven him."

Ixpec-Chitay is accused of driving the 2009 Volkswagen Touareg SUV that struck Walsh as she walked along the 300 block of Rose Hill Road. The car, which belonged to Ixpec-Chitay's employer, businessman Andrew Zaro, was found abandoned with front-end damage about a half-mile from Walsh's body.

Walsh, a Bronx native, was a beloved figure at St. Edward in Syosset, where she served as pastoral associate for nine years. Before that, she worked for six years as a teacher and campus minister at Our Lady of Mercy Academy, a Catholic girls high school in Syosset.

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As part of an effort to put pressure on Ixpec-Chitay to turn himself in, authorities have also turned up the heat on his family, the source said. They detained two of his relatives on violation of immigration laws and successfully prosecuted his younger brother, Miguel, for lying to police about phone conversations with Carlos.

Miguel Ixpec-Chitay, of Riverhead, was convicted in federal court last month on a felony count of making a materially false statement and will face up to a year in prison at his sentencing Tuesday in U.S. District Court in Central Islip, court records show.

Carlos Armando Ixpec-Chitay and his brother called several relatives and friends after the crash to ask for help, including one in California, according to trial testimony.

Miguel Ixpec-Chitay was arrested in September after telling an Immigration and Customs Enforcement officer he had not been in contact with his brother. But records showed 19 phone calls between the two on the day of the accident and the day after, prosecutors said.

"This case is about a lie," federal prosecutor Lara Treinis Gatz said at the trial, according to court records. "A lie that mattered."

According to testimony by law enforcement officials at his brother's trial, police on July 10 found Carlos Armando Ixpec-Chitay's iPhone in the woods in Farmingville, roughly 40 miles from the crash scene, court records show.

"We know there will eventually be justice," Dwyer said. "We're just not certain of when."