Could it be,she stole the gun from JM and was selling it on craigslist for drug money, etc. and he answered the ad to buy it and killed her instead ? Why have him go to her apartment,she could've met him anywhere!
(I think a better story would have been he answered an ad to purchase the gun and as he was looking at it and then it accidentally went off, as she was sitting in his car)
Although,I think an exchange of one hundred and eleven text messages in one day is a lot, just answering an ad to purchase something.
I'd love to know what the rest of the stories he gave were...
Do we know yet if she was killed where she was found or at the apartment ?