Police sources said a woman approached the passenger side of the car and asked Lincoln to roll down his window.
Lincoln believed that the woman had spotted him earlier at the Palmer Social Club, at 6th and Spring Garden, sources said.
The two began talking, but their conversation ended when a man jumped into the SUV, pressed a gun against Lincoln's temple and demanded money.
Lincoln handed over cash and some rings that he was wearing. The robber ordered Lincoln to drive him to another location; when Lincoln balked, the assailant pistol-whipped him, sources said.
Moments later, the robber, identified by police as Altariq Hutchinson, inexplicably turned to leave the SUV.
Lincoln, 55, a 25-year veteran assigned to the department's traffic division, pulled his own weapon and fired several shots, hitting his attacker in the torso, Vanore said.
Hutchinson, 23, of Edgewater Park, N.J., died at 4:24 a.m. at Hahnemann University Hospital, he said. Investigators found a semiautomatic gun at the scene.
Investigators questioned a second man whom they believe may have been involved in the incident, but hadn't charged him yesterday afternoon.
Sources said Lincoln believed that the woman who approached his car had set him up for the robbery. As of yesterday, she had not been located or identified.
Lincoln suffered bruises and cuts to his face, Vanore said.
He slumped in the back of a police cruiser, holding a handkerchief to his wounded face as investigators documented the scene just before dawn.
Authorities have posted a $15,000 reward for information leading to the capture and conviction of the thugs who wounded Campbell and killed Allen.