It's a tale as old as time, when the people feel the leaders representing them are not listening or going against their interests, riots happen. The same thing happened in Dublin when a foreigner stabbed multiple school children. Sure you can see it in LA right now, ironically for the opposite reason! (Not condoning it just that seems to be the reasoning)
I hope something changes, we've had similar rape cases down South and it feels like it could kick off any moment in a similar way, seems to be no control and government are dismissive and doing very strange things that's only stoking the fire (such as recruiting garda from refugee centres), we don't have access to the EU database on migrants so we can't even vet them by their own admission.
I don't know, it's worrying, people have every right to be angry but you really don't like to see this. Like you said, innocents could have easily been hurt. I wish I could offer an idea or solution but really no idea.
Adding that the Romanians in Ballymena are posting threats now on Facebook, so this might not be the last we hear of this..