More than 100 police officers and federal agents were looking for Sang Ho Kim, 64, whose car was abandoned Wednesday night near Cold Spring, N.Y., WNBC-TV, New York reported.
U.S. Marshals and the FBI assisted police agencies.
Residents in the search area were advised to lock their doors and to make sure keys were not left in vehicles.
Kim allegedly walked into the office of Savenergy Inc. in East Garden City on Long Island and opened fire Wednesday morning, the New York Daily News reported.
An employee, identified in a Newsday report as Yong Jae Shin, 25, of New York City, was killed and John Choi, the company's founder, was critically wounded.
Investigators said Kim, a Savenergy vendor, had a disagreement with the company.
David Lee, president of the Korean American Public Affairs Committee, said Choi was lucky to survive the shooting. Lee said his friend was shot in the forehead but the bullet missed his brain and did not damage his eyes.
The suspect's car was discovered in Little Stony Point Park at Cold Spring along the Hudson River about 50 miles north of New York City.
"We are in the process of trying to find the perpetrator of this heinous crime and we have an extensive manhunt taking place ... as we speak," Putnam County Sheriff Don Smith said. "We have a fugitive on the loose, we have someone who has committed a homicide potentially still in this area."