NEW YORK - Investigators are trying to piece together what caused a quiet loner laid off from his T-shirt designing job to ambush and kill an apparel company executive outside the Empire State Building.

Police say Jeffrey Johnson shot Steve Ercolino in cold blood in the shadow of the Manhattan landmark Friday, then was shot dead by police after he turned his gun on them.

Johnson spent hours in Central Park, photographing hawks and marveling over nature's beauty. Neighbors say he left home every morning in a suit despite losing his job a year ago and was always alone.

Relatives say Ercolino was a gregarious salesman beloved by his nieces and nephews.

Police investigating the killing are eyeing bad blood between the men from when they worked together at a garment district business.