A Bucks County lawyer was fatally shot by an unidentified assailant this morning as he arrived for work at his office in Northampton Township.

Eric Birnbaum, 51, a divorced father of two, was shot once in the back of the head at point-blank range, and was pronounced dead at St. Mary Medical Center, officials said.

First Assistant District Attorney David Zellis said the shooting occurred shortly after 9 a.m. in the parking lot of a strip shopping center along Buck Road in the Holland section of Northampton.

The lawyer had just wheeled his black Acura sedan into a parking spot and had taken a few steps toward his office when a man with a handgun approached from behind and shot him.

A co-worker who had just arrived and parked beside Birnbaum's car saw the suspect fleeing in a blue van. A vehicle matching the description later was pulled over on Bustleton Avenue in Northeast Philadelphia.

Zellis said a "person of interest" was taken into custody and was being questioned in Philadelphia by Northampton and Bucks County investigators.

Birnbaum, a member of the Pennsylvania bar since 1983, worked for Terry D. Goldberg Associates, which Zellis described as a small firm that handled civil cases, primarily personal injury and workers compensation cases.