There, in his headlights' path, was an unoccupied silver Honda Accord with Maryland plates. It was nose down in a small creek, the engine still running. Blood was smeared on the driver's side door, a child seat visible in the back. The man called 911.
The discovery launched a series of events and questions that propelled the case into one of the region's most high-profile and most perplexing murder investigations. Top officials boldly promised to catch Luna's killer, and law-enforcement officers worked diligently, certain they were hunting for someone who had killed one of their own.
But the focus soon turned to Luna's personal troubles, with federal sources leaking details of the prosecutor's debts and job difficulties, along with unproven theories of affairs and stolen evidence, to media hungry for answers. Luna had become a suspect in his own death.
Over the next several years, reputations were sullied, investigations allegedly botched and Senate inquiries made. A Pennsylvania private investigator has put forth hypotheses - based on evidence he claims to have found - implicating the FBI, and book authors suggested deadly federal informants were to blame. And now, nothing.
Five years after the case was opened, it's gone cold. No one has been caught, no culprit has been identified. A spokeswoman with the federal office now in charge of the investigation, the U.S. Attorney's Office for the Eastern District of Pennsylvania, wasn't even sure whether it was still overseeing the case, it had been so long since anyone inquired. She eventually confirmed that the FBI case is still open but would say no more.
The uncertainty is frustrating to those who knew Luna.
"I was fearful that he had been killed in relationship to the job, which is what everybody thought" initially, said Lynne A. Battaglia, who's now a Maryland Court of Appeals judge. She hired Luna in 1999, when she was the U.S. attorney for Maryland.
"I don't know now, I have no idea now," she said, "It will remain a mystery to me."
Many people don't want to talk about his death, preferring instead to remember his life. His wife did not respond to a letter or phone calls from The Baltimore Sun. His father, who as recently as last year tried to stir some developments in the case, declined to comment. So did the coroner who ruled the death a homicide, a view, he would only say, he still stands by.
And many of Luna's former colleagues refuse to speak publicly, their silence motivated in part by a desire to spare his family additional pain. They also hesitate to acknowledge a terrible possibility: that Luna killed himself either deliberately or accidentally, a theory raised by anonymous federal law enforcement sources who noted that the 36 stab wounds were superficial. The odd circumstances, which included cash strewn about his car, make it difficult for some to believe his life ended in suicide.
Jonathan Paul Luna - "Joey" to his friends growing up in New York - was raised in a rough section of the South Bronx, in the shadow of Yankee Stadium. His father struggled to make a living in the restaurant business, while his mother stayed home to care for their two boys, Luna wrote in a 1991 letter to the New York Times, defending his Mott Haven neighborhood as a place with "much hope and promise."
Like his parents, Luna worked hard, though he remained a friendly and affable kid, and a loyal Yankees fan. He earned an undergraduate degree from Fordham University in New York, then attended the University of North Carolina's law school, graduating in 1992.
He married his wife, Angela, in 1993, during her last year of medical school, and worked as an attorney in Washington for several years after that, first in a private firm, then with the Federal Trade Commission.
Next he returned to Brooklyn, working as an assistant district attorney, before applying for the federal prosecutor's job in Baltimore.
"He had a really vivacious personality, peppy, excited, full of vigor," Battaglia remembers. "He really wanted the job; he really wanted to be an assistant U.S. attorney."
Once hired, he and his wife moved into a home in Elkridge, where they would live with their two young children and his mother-in-law. He was well-liked in the Baltimore office, described as the sort of person who remembered details about others and frequently inquired about their families. He still sent Christmas cards to colleagues who moved on to other jobs.
But as time passed, he faltered professionally. Co-workers said he was in disfavor with Battaglia's successor, Thomas M. DiBiagio. DiBiagio publicly denied that Luna was in trouble but privately confirmed it to others in the office, according to The Sun and other news media. Fearing he was about to lose his position, Luna hired former federal prosecutor Andrew C. White for guidance and legal representation.