On October 31, 1986, Kim asked 49-year-old Kim Gye-hwan, a friend of hers who also lived in Sindang-dong, to go to the bathroom together. Not long after, Gye-hwan fell down the stairs after drinking a cyanide-laced beverage. She was transferred to a nearby hospital, but died suffering from severe cramps and breathing difficulties. Her necklace and ring had been stolen, but police found no evidence connecting Kim Sun-ja to the crime. On April 4, 1987, Kim asked 50-year-old Jeon Soon-ja, a creditor who lived in Sindang-dong, if they could ride the bus together so she could get some money in
Yeongdeungpo. She borrowed 7 million
won, and the two women then boarded a bus. While riding on the bus, Jeon started complaining that her drink had been poisoned with something, and fell from her seat. She was taken to a nearby hospital, but soon after died. On February 10, 1988, she suggested to 46-year-old Kim Soon-ja, another creditor based in Sindang-dong, that they go to a coffee shop together so Soon-ja could receive money from a debtor. Kim had borrowed 1.2 million won from Soon-ja some time before, and agreed to go with her. Both waited for the debtor to come out, but after he didn't show up, they decided to leave. Soon-ja then drank a poisoned
Yulmu-cha, which caused her to vomit on the way home in the taxi. Kim said that she would get better if she had more of the healthy drink, but suggested that they get out of the taxi first. Soon-ja, already suspicious of her behavior, ignored her suggestion. Kim later repaid her, and even visited her house to ask if she was alright. On August 8, 1988, Kim met her 46-year-old cousin, Son Si-won, who lived in
Changsin-dong, at a coffee shop in
Sungin-dong. Kim proceeded to borrow 484 million won, ostensibly for a deposit required to buy a house, and then gave her cousin a poisoned drink. Son Si-won suddenly collapsed while riding the bus toward
Seobinggo-dong, was taken to the hospital, and subsequently died. == Arrest and execution ==