Regarding the fourth victim, Ye Qing's death still shook the police and caught them off guard! They never expected that the murderer of the Hasty Murder Case could kill another staff member of the pharmaceutical factory in such a short period of time!
According to the updates from the scene, Ye Qing, who was the current chief of the research and development department, died in his private car. Although the autopsy report wasn't out yet, according to the speculation at the scene, he died of gas poisoning! Someone had connected the exhaust pipe to the car with a hose, then started the engine, which led to the deceased's death.
As there was no struggle on the scene, the police speculated two possibilities. First, the deceased died of suicide. Second, the deceased was murdered and was unconscious before he was poisoned to death.