I don’t want to get moderated, so I’m not going to offer opinions, just help with the definitions.
First degree murder is a premeditated, intentional killing. If you stalk them for a while then kill them, or have plans on exactly how and why you will kill them, that is first degree. Serial killers fall under this category.
Second degree murder is when you don’t plan it, but it is intentional. When you are in an argument with someone, and then grab a gun and shoot them, that would qualify. It was very heat of the moment, not much consideration.
First degree murder is also called manslaughter. It isn’t intentional and it isn’t planned, but someone did die because of your actions. Some examples would be if you backed your car into someone, someone jumped in front of your car, you tripped and pushed them off a cliff (you may need some strong evidence to prove it wasn’t intentional), or even if you accidentally gave them something they were severely allergic to.