His weight is down. He's not eating or sleeping well.

Folded in the pocket of his crisp dress shirt is a prescription slip from his doctor. "Play baseball," it instructs.

Two months after the execution-style slaying of his best friend outside the law office they shared, Bucks County lawyer Terry D. Goldberg is stressed and frustrated.

The daylight Feb. 11 shooting death of Eric Birnbaum, Goldberg's pal since age 14, remains unsolved.

The $10,000 in reward money he offered sits unclaimed.

The once-daily calls from detectives on the case - whose efforts Goldberg praises - are now weekly chats.

Worse, says Goldberg, Birnbaum's killing seems to have fallen off the public radar.

He has, therefore, chosen to talk about a loss once too raw to discuss. Silence, he says, won't find his friend's killer.

"Somebody out there knows something, someone besides just the shooter," he said Friday. "I hope that the person or persons would have the courage to step forward."

About 9 a.m. that day, Birnbaum, 51, was executed by a man described only as white and wearing a knit hat and sunglasses. Birnbaum had just stepped from his black Acura in the parking lot outside Goldberg's four-lawyer firm.

The scene is wide open: a strip shopping center along busy Buck Road in the Holland section of Northampton Township. Yet no one provided a good description of the shooter or said whether he ran or drove off.

A female coworker with Birnbaum in the parking lot told police the gunman "appeared out of nowhere" and shot the lawyer in the back of the head. She fell in terror and saw nothing more.

An employee in the law office reported seeing a blue van speeding away. Police stopped a similar van on Bustleton Avenue, but the driver was released after officers confirmed his alibi.

A surveillance camera mounted near the law office proved worthless; it did not record.

Goldberg has heard the theories - disgruntled client, mob hit, mistaken identity - and has doubts about each one.

First Assistant District Attorney David Zellis, who is overseeing as many as 10 township and county investigators on the case, said Friday there was nothing new to report.

"We are continuing to work diligently," Zellis said. "Terry Goldberg and the firm have been very cooperative with the investigation."

At the time of the shooting, Goldberg said, he was home, three minutes away, when a secretary called, so hysterical he could make out only selected words.

"Parking lot . . . Eric . . . shot . . . office." He threw on a pair of sweats and arrived to see Birnbaum still there, his blood pooled behind his car. Birnbaum died a few hours later.

They had been friends since high school and had attended college and law school together. Goldberg had introduced Birnbaum to his wife (though they later divorced), served as his best man, and was his daughters' godfather. In June, after years of offers, Birnbaum finally agreed to join Goldberg's personal-injury law firm.

Birnbaum's reputation - friendly, generous, hardworking, doting father - offers no clue to his slaying.

"Eric didn't have a personal enemy," Goldberg said. "There was no reason for anyone to dislike Eric."

The firm has up to 300 active cases - almost all involving personal injuries. Investigators have said they were looking through all of Birnbaum's cases, checking for possible disgruntled clients.

Goldberg considers that unlikely. Birnbaum was known as a passionate advocate who handled each case with care.

"The more I've looked through the cases that he handled, it makes me embarrassed by comparison. He is that meticulous; he has a dated note for every single conversation he had," Goldberg said.

What about a defendant angry over being sued? Another stretch, Goldberg said.

"Eric shared my thoughts that we draw the line [on damages] at insurance-company dollars," Goldberg said. "I've never tried to take someone's house, never tried to take their personal assets."

He said he had received no threats and knew of none against Birnbaum.

Might the killer have targeted someone else - Goldberg, perhaps - and mistakenly shot Birnbaum instead?

In photos, Birnbaum is taller and heavier than Goldberg, with lighter and less-chiseled features. Yet they were the same age, worked in the same place, and each had a full head of swept-back hair.

"From the front, no one would mistake us," Goldberg said. "But from behind, in a suit, pulling up to a law office, graying hair. . . . "

Then he dismisses it.

"The police have really put that thought in my head; I never really thought it."

Police have asked Goldberg whether Birnbaum might have been in debt to anyone unsavory and was perhaps embarrassed to ask him for a loan.

"I told them he wasn't embarrassed to ask me when he was buying a house," Goldberg said, "and he paid back every bit of it."

Until the killer is caught, life goes on uneasily.

The law firm reopened within two weeks of the shooting, Goldberg said, albeit with added security.

"Coming back and seeing Eric's name still on the door, unhappiness was the overriding feeling, not fear that the [killer] would be coming back here," Goldberg said. Still, the outside doors are kept locked - a first for his firm.

He also looks out for Birnbaum's two college-age daughters, from being an open ear to fighting an insurance company for their father's worker's compensation benefits.

"I'm worried about my employees. I'm worried about Eric's kids," he said. "I'm trying to be everybody's support group, but I'm not sure I've grieved in the way I should. I tear up a little and just wipe it away."

By speaking out, he said, he hopes someone who knows who killed his friend will call police.

"Not just because there's a reward fund out there," he said. "But because two girls, my goddaughters, have lost their father, a tremendous guy, in a senseless way."

To Provide a Tip

Investigators ask anyone with information to call Northampton Township police at 215-322-6114. Alternatively, tipsters may remain anonymous by calling the Citizens Crime Commission at 215-546-8477 (TIPS).