Just ask this woman. Jealous of her boyfriend's other object of affection - his wife - a woman contacted a private detective in Tokyo (they're Japanese) and paid him 1 million yen in cash to kill the other woman.
Being a very scrupulous man of high moral character and understanding the importance in society of dating an unmarried man, the private detective accepted the job. He suggested he could accomplish the task by "chasing the [woman] on his motorcycle and spraying her with a biological agent in a tunnel."
Bear in mind the adage, "The best laid plans of mice and men often go awry." The hitman did not, in fact chase the woman and spray her with a biological agent. He failed at the job for which he was hired. So the woman who contracted with the hitman did the sensible thing. She called the police and told. The police took this very important matter very seriously and arrested the woman and the hitman. They then located the target and insured she was safe and sound.