yes but remember it can take only minutes to form intent
and you can still form intent while in a rage
I think he snapped when he talked to her & she said she was 'having a good time' and that she immediately left because he was angry. I think he was planning it while she walked home. I want to see those texts. JMO
I think Canadian law is different in the sense that there has to be a clear intent to commit murder. It cannot be something that happens a minute prior to the murder ... in Canada, the decision to murder someone a minute prior to committing murder is considered second degree murder.
If he had prepared plastic and tools to cut her up between the time that she went to the party and the time she returned, that constitutes first degree murder.