Duterte, speaking at a power plant inauguration on Thursday, January 26, assured South Korean investors in the audience that the killers will go behind bars.
"I can assure you, those responsible are known to us already, and they will have to go to prison and I will see to it that they are sentenced to the maximum," said Duterte.
Toward the end of his speech, Duterte specified that he believed the killers are policemen.
"Tang ina kayong pulis, bantay kayo, hindi ko kayo papalusutin (Police, you sons of bitches, I won't let you get away with it). You will suffer. Maybe I can send your heads to South Korea," said the President.
To the South Koreans present, he apologized in behalf of the Philippine government for Jee's murder.
"I apologize for the death of your compatriot. We are very sorry that it had to happen," said Duterte.
At the time of his speech, the Senate investigation into Jee's murder was ongoing.
Jee's death has shaken the Philippine National Police, as critics point to it as proof that corrupt policemen are using Duterte's anti-drug campaign as a smokescreen for other crimes like kidnap-for-ransom.
Cops who abducted Jee were told he was the "right-hand man" of a drug lord named Albert Chua.
However, Jee's abductors demanded a P5-million ransom for his release. A National Bureau of Investigation probe found that Jee was murdered inside Camp Crame, the PNP's own headquarters.
Duterte's threats against police suspects in the Jee murder case are in stark contrast to his defense of police suspects in another alleged murder case – the killing of Mayor Rolando Espinosa Sr of Albuera, Leyte.