A federal prosecutor who disappeared as he was preparing to conclude a drug case against a would-be Baltimore rap artist and another man was found beaten, stabbed and shot in rural Pennsylvania yesterday, and top federal officials vowed to track down his killer.

There was no immediate indication that the slaying of Assistant U.S. Attorney Jonathan P. Luna was connected to this week's trial in U.S. District Court, where two Baltimore men were accused of dealing heroin from the Hampden studio of their upstart music label, Stash House Records.

Luna, 38, told a lawyer in the case Wednesday night that he was returning to the courthouse to prepare documents for an expected guilty plea. When Luna failed to appear for the hearing early yesterday, authorities realized he was missing. By midday, officials determined it was his body and car that were discovered about 5:30 a.m. by police in Lancaster County, Pa.

Luna's 1999 Honda Accord was found nose-down in a small creek beside a well-drilling business. His body was found lying in a field near the blood-splattered car. Law enforcement sources said Luna had been severely beaten and repeatedly stabbed, and Pennsylvania State Police said in a news release that he died as a result of stab wounds.

Lancaster County Coroner Barry D. Walp said last night that Luna also had been shot. He declined to say what the cause of death was.

In Baltimore late yesterday, Maryland's chief federal prosecutor said those responsible for Luna's death would be found.

"We will find out who did this, and we are dedicated to bringing the persons responsible for this tragedy to justice," U.S. Attorney Thomas M. DiBiagio said. "That's a commitment from me. That's a commitment from every law enforcement officer in the state of Maryland."

DiBiagio and Jennifer Smith Love, acting special agent in charge of the FBI's Baltimore field office, called on the public for help in solving the case during a brief news conference outside the federal courthouse in downtown Baltimore. They did not respond to reporters' questions, but urged anyone with information or tips to call the FBI field office at 410-265-8080.

In Lancaster County early today, more than 100 Pennsylvania State Police cadets were enroute to the crime scene to comb the area for evidence before an anticipated snowfall.

In Baltimore, investigators were working yesterday to retrace Luna's last steps to help find answers to the key questions: Could Luna have known his attackers, or was he abducted and attacked by strangers? How did he wind up in rural Pennsylvania, and were any stops made along the route? And was another vehicle, serving as a getaway car, involved?

Authorities also were combing through Luna's work files to determine whether the motive behind his killing could be found in any of the cases he was prosecuting.

Luna joined the U.S. attorney's office in Baltimore four years ago, under then-U.S. Attorney Lynne A. Battaglia. He had handled a range of cases, but among his more notable was the prosecution this year of a Navy physicist who was accused of trying to seduce a teen-age girl on the Internet, but who claimed that he was only engaged in online fantasy.

Late last year, Luna won convictions in a string of violent Baltimore County bank robberies in a curious trial that produced its own mystery: At the end of the trial, authorities discovered that more than $36,000 in cash disappeared somewhere between the courtroom and the government storage area used to hold sensitive evidence during trials. That case was never solved.

This week, Luna was the lead prosecutor in the drug trial against Deon Lionnel Smith, 32, and Walter Oriley Poindexter, 28, who tried to make it in the rap music industry. The two men admitted yesterday to selling heroin from the recording studio of Stash House Records on West 36th Street in Hampden. They had been in federal custody since spring and remained jailed yesterday.

Late Wednesday, three days into the trial, Smith and Poindexter had tentatively agreed to plead guilty after setbacks in the case both for the defendants and for the government surrounding an FBI witness, Warren Grace, who had secretly recorded drug transactions with the defendants but who also had escaped his electronic home monitoring while helping authorities with the case.

Poindexter agreed to plead guilty to three counts of heroin distribution, and Smith agreed to plead guilty to one count of heroin distribution and to possessing a firearm, a Ruger 9 mm pistol, during a drug transaction. In exchange, Luna agreed to drop drug conspiracy charges against both men that could have meant much longer prison sentences.

Luna also agreed during a meeting late Wednesday afternoon with Poindexter's attorney, Arcangelo M. Tuminelli, that the government would not try to introduce evidence at sentencing that Poindexter was responsible for the fatal shooting Jan. 22, 2001, of Alvin "L" Jones, who was suspected of burglarizing one of the group's stash houses.

Tuminelli said yesterday that he left the federal courthouse about 6 p.m. Wednesday. He said his client was eager to have the deal settled and called it "implausible" that either defendant would have wanted Luna harmed.

"These two defendants had every incentive to want to see Jonathan Luna show up here today," he said.