1) timing: Apparently, there is a need to shut him up. It is exactly due to 这个敏感时期, Bo's wife did not want someone to talk about their secrets. So the timing actually makes sense.
2) Motive: to prevent him from revealing some secrets.
3) 手段: Poisoning is the best to ensure the victim is dead. The death is quick so that he will not have time to talk to anyone. In addition, poisoning can be disguised as heart attack or other nature death so that no investigation is needed. Car accident cannot guaranttee death. In addition, any violence related death, e.g., murder by assassin, will be investigated automatically.
