okay, another theory - I have NO reason to believe it's true, other than to throw it out there for speculation
What if the shooter were someone the family knows? What if someone in the family were having problems with this person for reasons ranging from stalking to an argument over whether something was stolen? What if this person is a bf (current, former or otherwise) of Jayme and he decided to take (rescue) her? That would incite enough anger/emotion for a physical confrontation which got out of hand. Mom and dad protecting her from being taken. Or, again - speculation - what if Jayme was sneaking out to meet someone and they got caught and it got out of hand? So many scenarios, it makes one's head spin, almost.