AS THE CO-OWNER of a landscaping supply business, James Stuhlman helped life to grow.

But on Thursday night as he was out walking his dog in his Overbrook neighborhood, Stuhlman's life was cut short by a heartless gunman, according to police.

At 8:39 p.m., officers responded to reports of a person with a gun on Woodcrest Avenue near 64th Street. When cops arrived, they found Stuhlman, 51, lying on a curb with a single gunshot wound to his chest.

He was taken to Penn Presbyterian Medical Center, where he was pronounced dead at 8:58 p.m., police said.

Although initial reports Thursday night said Stuhlman may have been the victim of a robbery, yesterday police said the motive for his slaying remains unknown, as does the identity of his killer.

Stuhlman lived in a leafy and quiet neighborhood on Woodcrest Avenue near 64th Street, just a block away from where he was slain. His home is less than two miles from where Mayor Nutter lives.

When reached by phone yesterday, Stuhlman's family politely declined to comment.

Online records show that Stuhlman is co-owner of Hilltop Distributors Co., a landscaping supply business in Media.

Yesterday, the phone at the business went unanswered.

Anyone with information on Stuhlman's slaying is asked to call the department's tip line at 215-686-8477.