I don't put any stock on the car accident as how she died. It can be really hard to have to tell someone their family member has died and many, many people will start off by saying "There's been an
accident" rather than immediately going into "I'm sorry to have to tell you, but your wife has been found murdered". The murder part comes later, but people generally try to break it gently. Some people (especially professionals or experienced in this) will pick up on whether the receiving person is ready to hear more details and waits for them to ask. If they don't ask, they may or may not explain further, but no details. It's may have been easier and/
or kinder to let people assume 'car accident' and go from there. I can also picture BB telling his mom it was an accident and she herself inferred 'car'.
A few ways misinformation gets moved along.
Personally, I think it would be kinder to tell anyone who will immediately be traveling to be with their loved one or family, to let them think it's an accident and not a deliberate murder. Thinking it was an accident would be stressful enough to be stuck with while coming home, but your wife being murdered - brutally murdered - would be extreme.