It isnt frivolous - a significant event occurred that was not normal and the claimant states he suffered mental and physical injury
It isnt vexatious - as above, and in many countries courts apply it to litigants who repeatedly claim or continue to claim unreasonably. This is an initial claim with no evidence of previous claims
That still leaves the Courts to decide whether to make a judgement in his favour, or the defendants to decide they want to settle before a hearing....