Police said Tuesday that Cha Cheol-nam, the suspect in the killing of two brothers and the stabbing of two others in Siheung, Gyeonggi Province, planned the attacks in advance.

Based on CCTV footage, financial records and phone data, authorities concluded that Cha, a 56-year-old Chinese national of Korean ethnicity, began preparing in early May, purchasing weapons and tracking his victims ahead of the slayings on May 17.

They say the motive was financial, quoting Cha as telling police he acted out of anger after the two victims failed to repay a 30 million won debt, which amounts to about 22-thousand U.S. dollars.

Two days later, they say he stabbed and injured a convenience store owner and his landlord, claiming they had disrespected him.

Police say they conducted a psychological evaluation for antisocial personality disorder and psychopathy but concluded that Cha is not a psychopath.

He is now set to be formally handed over to prosecutors and will most likely face charges of murder and attempted murder.