New York ? Robert Reuland parked his black Mercedes station wagon at a meter and walked across Ralph Avenue to a half-dead strip mall.

On a cloudy February morning four years ago in this bleak stretch of south Brooklyn, a 16-year-old boy leaned across a bodega counter and fired a .45 caliber derringer into the Lebanese immigrant owner’s chest. Khalil “Pop” Hussein died where he fell.

Reuland, then an assistant district attorney, put the killers in prison. The crime faded from the headlines and the bodega closed down.

“This is a place where a man exited the world. You would never know it,” Reuland said. “We forget very well in New York City.”

Reuland hasn’t forgotten.

He published his first novel after the Hussein killing, infuriated his boss and lost his job. Now he’s revisiting the murder in a new novel and his troubled relationship with Dist. Atty. Charles J. Hynes in a lawsuit set for trial this month.

The Hussein slaying figures prominently in “Semiautomatic,” out this month. The book brings back protagonist Andrew Giobberti, a bitter and burned-out assistant D.A., to prosecute a thinly fictionalized version of the 2000 killing.

“Semiautomatic” draws a bleak portrait of a Brooklyn criminal justice system peopled with dishonest cops, careerist prosecutors and killers who get away with murder. Reuland’s cynical take has won him positive reviews.

He also says his writing cost him his beloved job as a prosecutor and set up the legal battle with Hynes.

Reuland’s troubles began after publication of his first book, “Hollowpoint,” in 2001. He was quoted in New York magazine saying: “Brooklyn is the best place to be a homicide prosecutor. We’ve got more dead bodies per square inch than anyplace else.”

State Sen. Marty Markowitz, now borough president, complained to Hynes about the blemish on Brooklyn’s image. Reuland says he was then demoted and forced to resign.

Reuland sued Hynes in federal court. He claims the district attorney violated his First Amendment right to free speech when he forced him out because of the interview and the content of his book.

“As a novelist and as a lawyer, I have an obligation to stand up for the sanctity of protected speech,” said Reuland, 40. “You shouldn’t be punished for publishing a book.”

Robert Reuland, a novelist and former Brooklyn assistant district attorney, visits an old crime scene in New York's Brooklyn borough. Reuland is suing the Brooklyn D.A. for forcing him to resign because of comments made in his novel Semiautomatic about local crimes and the D.A.'s office.

The city’s law department wouldn’t comment. But the city argues in its legal filings that Reuland’s statements about Brooklyn homicides don’t merit First Amendment protection because they merely promoted his book and did not address a topic of public interest. In any case, the city says, Reuland was demoted for incompetence and asked to resign because of his bad attitude after his new posting to a part of the office covering low-crime sections of Brooklyn.

For his part, Reuland takes shots at his former boss. He charges that the district attorney’s office sought indictments in cases considered “easy wins” just to buttress its conviction rate, while dismissing felony cases or reducing them to misdemeanors to sanitize statistics on serious crime.

Hynes, a veteran New York pol who has been D.A. since 1990, faces a potentially tough race next year. He likely will take the stand if Reuland’s case goes to trial. A spokesman for Hynes wouldn’t comment on the lawsuit.

Trial or not, in his writing Reuland draws an unflattering portrait of the D.A.’s office, loosely based on the real thing. By the end of the first book, Giobberti has been demoted to the unglamorous appeals bureau by the politically minded D.A. In “Semiautomatic,” he gets a chance to work his way out by prosecuting the bodega slaying.

“Semiautomatic” was called “one of the better crime and punishment tales we’ve seen in a long time,” by the Rocky Mountain News.

The Washington Post called “Hollowpoint” “an unforgettable journey into a fallen hero’s psyche … using language so carefully cadenced it borders on poetry.”