We've already got a serious problem with over-escalation here. All this will do is make the people most able to deal with the problem too afraid even to acknowledge it.
Don't look, don't think, just call the Miniluv.
Get in with the police force (in all liklihood they would welcome his connection to the pupils) and provide suppor through that medium; that seems a more logical approach (what he did sounds like a half cocked investigation of his own - which is a bad idea full stop anyway :D).
As it is he will almost certainly be let off with a caution (provided nothing else is found) - but siezing it is all but mandatory. If nothing else to ensure the images are correctly destroyed.
Such is the sad but true we now find ourselves in.
There seems to be a common attitude among school administrators that anything involving students is their business. It is not.
You also complained about getting downmodded, which is why you're at 0 here.