I can shed some light on this, 15 years of practicing criminal law in Florida, 5 as a prosecutor 10 as a defense attorney
No such thing in Florida as Vehicular manslaughter. It's strictly recognize as a "Vhom" as we call it, but essentially its the same thing as manslaughter.
If this was an intent issue, IE the state could prove that he actually intended to kill these people using his car, then it would be charged as murder.
This is the exact language of the Statute "782.071 Vehicular homicide.—“Vehicular homicide” is the killing of a human being, or the killing of an unborn child by any injury to the mother, caused by the operation of a motor vehicle by another in a reckless manner likely to cause the death of, or great bodily harm to, another."