I'm waiting for the probable cause affidavit but I think that's definitely one of my 2 theories. I think it's really possible he lost it (maybe was high or drunk), shot her, and then didn't have any plan for what to do after. He may have sat with her, realized it was too late to call an ambulance and say it was an accident, panicked, took her purse, and tried to destroy what he took later on to hide his tracks. Sometimes the simplest explanation is the right one.
There are just a few things that are still hinky to me. After the first hearing, when the media spoke to the prosecutor, he said something vague like "we want to make sure the person who did this crime is held responsible" when asked about why the arrest warrant would be sealed. I expected him to say something stronger - "We want to build the strongest case possible against Mr. Hagan" or something like that. It just struck me as odd if everyone thought it was a DV incident and the sole person responsible was in jail.