The shootings kicked off a manhunt for Kim -- described as a "disgruntled contractor" -- who had been working as a vendor for lighting company Savenergy. He reportedly fled the scene in a white Honda pilot with New York plate number FMA 3648.
"At this point and time we believe that this suspect is armed and very dangerous," Nassau County Police Chief of Department Steven Skrynecki told reporters. "Right now we are involved in a very massive hunt for this individual."
Skrynecki said the gunman appeared to be targeting his business associates over a "bad business deal."
"There was some disgruntlement between him and the company that he was attacking," he added.
Nearby schools, including Nassau County Community College and Hofstra University, are no longer on lockdown, though no one is currently allowed to enter the mall.
"We're very confident he's not in this immediate area now," police said.