I submit that the actions of those boys was sufficiently un-Catholic that they should be permanently expelled from the school. “Our students do not do that, and if they do that, they are no longer our students.” Over and above any criminal charges and civil judgements, both of which I think should be forthcoming.
Expulsion isn’t impossible, but general practice is to try and keep the student in the school and teach them to do better next time - not just pass the problem on to somebody else knowing that nothing will be done to correct their behaviour at all if that happens - with expulsion only being used with repeat offenders. These may well be repeat offenders but if this is their first serious breach, suspension is most likely.