Here's one possible way it went down: His wife kills him and hides the body. The university then fires him because he doesn't show up and won't respond to any messages. Eventually the university gets suspicious and calls the FBI. The FBI raids the apartment because they think it might be a crime scene. The reason its the FBI and not local cops is because the university mentioned that he was Chinese and working on sensitive research so the feds step in, due to them perceiving some possible espionage angle.
I am not saying that definitely happened, but it's a narrative which more or less fits the facts.
I am not saying that definitely happened, but it's a narrative which more or less fits the facts.