In his first month on the job, Assistant U.S. Attorney Jonathan Luna (search) brought federal gun charges against three convicted felons. He would win them all.

Next, the young prosecutor sent four cocaine traffickers to prison. He won his first 14 cases -- judges sentenced the defendants to decades of prison time.

In four years, from the time he arrived in Baltimore (search) until his body was discovered last week in a Pennsylvania creek, Luna had a hand in more than 120 federal cases involving some of the region's seediest characters.

Federal agents have begun asking questions about Luna's personal life, but they say they are still mining the list of drug dealers, armed convicts, bank robbers and child pornographers he prosecuted for any potential link to his killing. FBI spokesman Larry Foust said investigators have not come up with a motive for the slaying and are open to all possibilities.

Luna's father and his friends tell The Associated Press they saw nothing to suggest the 38-year-old father of two had anything sinister or amiss in his personal life.

"He was very happy," his father, Paul D. Luna (search) of Columbia, said Sunday.

His death, friends and family are convinced, must be connected to his work. His case list includes the breakup of a bank robbery ring, a conviction that sent an Ecstasy dealer to prison and the upcoming sentencing of a child sexual predator. In the bank robbery ring, Luna won a conviction but more than $36,000 in cash disappeared between the courtroom and the evidence storage area. The money was never found.

Luna never expressed fear about his work or of the people he was putting in prison, friends said. He spoke with pride about his job and empathized with both victims and suspects.

"He was very passionate," neighbor and friend Dana Stango said. "He was just upset there was so much bad stuff going on in the world."

Even as a law student, Luna had lofty ideas of what attorneys should be. "We're in this for justice," classmate Winston Crisp remembers Luna saying.

FBI agents asked Luna's father whether his son had any private relationships or money problems that might have contributed to his death. He said he didn't know of anything like that.