Police are currently seeking the whereabouts of an 'old friend' of the victim of a brutal "planned, professional murder" that took place earlier this week on Long Island, The New York Daily News reports:

A popular Long Island horse-riding instructor was killed when bullets tore through a window in the dream home he built with his longtime partner. Ross Reisner, 50, and Kevin Murray were sitting on a leather couch in the living room at their house in Setauket, L.I., at about 8:45 p.m. Tuesday when the shots were fired.

Detectives were seeking to question a longtime friend about the slaying, Reisner's grieving family told the Daily News.

“He was an old friend and now this craziness,” Ian Reisner, the slain man's brother, said as he sat shiva at his mother's midtown Manhattan apartment. “There was something weird going on, some bad blood.”

The friend had known Reisner for over 20 years and had a beef with him, Reisner's brother said.

Reisner's brother has also said the weapon used to murder his brother was a "high caliber" weapon, a far cry from "Dad's pistol under the pillow." Reisner's partner was grazed during the barrage of bullets that came through their living room window. A neighbor reported hearing one shot fired followed by six additional shots after a brief pause. Police officials say they have information that leads them to believe this was a targeted attack, though they have yet to release any details that might shed additional light on the case. Neighbors and friends meanwhile remain stunned by the horrific murder.

Watch an ABC News report on the slaying AFTER THE JUMP…