Parañaque City police chief Superintendent Ronald Estilles said the suspect, whose cartographic sketch was released the other day, was an employee of another gun store.
However, Estilles has refused to provide further details so as not to jeopardize their operations.
Helper Rex Dorremon, 27, was killed when some six men robbed the gun store and firing range of Weapon System Corp. They carted away 50 guns.
According to the gunsmith who was hurt in the heist, one of suspects went to the store last Friday to inquire about a purchase had introduced himself as an employee of another gun store located in Cavite.
The suspect also told the cashier that he had purchased barrels of a caliber .38 pistol from a gun store at a mall.
Police said the suspect was one of the gunmen who shot Dorremon.
"We already went to the address of the gun store where the suspect said he was employed," Estilles said in a phone interview with The STAR.
The police chief said they found no one at the establishment, except for the caretaker, who verified the purchase made by the suspect at a mall by showing them the receipts.
"Although our lead is strong, we are not discounting the possibility that the suspect could have mentioned where he was working to mislead us," Estilles said.
Police also suspect the victim knew the suspects since he allowed them to use the firing range even without a security guard around.
Estilles said they will conduct follow-up operations so the suspect and his cohorts could be arrested.