[grahn]

Most likely for the same reasons almost all crimes of this sort happen. He made a pass on her that wasn't well received, things got out of hand, emotions took over and at some point he either injured or killed her in the heat of the moment, then panicked and tried to cover up the situation.

Violent crime is rarely based on rational, well reasoned acts. I wouldn't try to read too much logic into it.

[dmix]

Do you have any data to support the claim that most crimes of passion involve "him making a pass at her"? This seems like an obvious narrative for a TV show but this is merely one of hundreds of possibilities that could result in her accidental death.

[grahn]

My "most" claim was more generic, in that they are situational, triggered by emotions (and lack of emotional control), and most often between people that know each other. Him making a pass at her is merely my conjecture of how that might have happened in this particular case, based on the circumstances that have been reported.