From Nevada statutes on homicide:
http://www.leg.state.nv.us/nrs/nrs-200.html#NRS200Sec020
"Manslaughter is the unlawful killing of a human being,
without malice express or implied, and without any mixture of deliberation."
"Malice: Express and implied defined.
1.  Express malice is that deliberate intention unlawfully to take away the life of a fellow creature, which is manifested by external circumstances capable of proof.
2.  Malice shall be implied
when no considerable provocation appears, or when all the circumstances of the killing show an abandoned and malignant heart."
To prove just
manslaughter, the prosecution would have to prove that
malice (either express or implied) existed in EN that night.
Obviously, the #2 definition of malice (implied malice) does not apply here it's clear there was considerable provocation.
That means that definition #1, express malice, is what they would have to prove manifested by external circumstances capable of proof.
"First Degree Murder:
1.  Murder of the first degree is murder which is:
(a) Perpetrated by means of poison, lying in wait or torture, or by any other kind of willful, deliberate and premeditated killing;"
"Willful, deliberate and premeditated" and "angry/emotional/panicked" don't see to be compatible with each other. IMO.
There is
no way this case rises to the level of first-degree murder.
Possibly manslaughter, but I think EN's got a pretty good chance at an acquittal or a hung jury. Especially if the Meyerses keep changing their story. Or if the school surveillance footage shows no driving lessons. Or if other evidence comes to light that shows that the Meyerses were in fact stalking EN, lying in wait for him at the school, and trying to kill him or harm him.