Just having a quick read through CAO 20.16.3, seven if it is a six seater, or nine if it is a seven seater. I though there was a requirement for these seats not to be adjacent to an emergency exit, but can't seem to find the reference, other than for infants.
Cheers, HH.
PS: If you were witness to the incident and are concerned about it, report it.
Reference: CAO 20.16.3, section 12 & 13 apply.