Re: death of 15 year old son due to epileptic fit???
Sudden Death in Epilepsy (SUDEP) is not easy to tell unless they know the person had suffered from epilepsy. Often times it's suffocation, or if the patient asphyxiates if they throw up and can't come to due to the seizures effects. It look's intentional if the team doesn't look deep enough.
Tissue sample will tell time of death. the other parts of the question are hard to answer. SUDEP is still being studied. There is a lot they don't know about the "why" part.
As for your youngest, the other thing to consider is his age. Growth hormones are kicking in, he is in a mixed up state of life. So social pressures may also have an effect on behavioral actions.
For SUDEP risks, some of the key indicators are 3+ medications, poor upkeep, overweight, failure to see doctors, poorly controlled seizures, not enough sleep.
SUDEP is a SMALL percentage (around 1-1.5 of the 3000 deaths from one data group; if I recall correctly... it may be a little lower).