The missionaries have already long since returned home. The LDS church spokesperson indicates there will be some sort of penalties though of course the details could not be discussed publicly. If civil or criminal remedies are pursued and the young men are convicted, I can guarantee that the upshot will be some sort of disfellowshipment or excommunication: this is pro forma within the LDS Church. You cannot remain an LDS church member in good standing if you are convicted of any sort of serious crime (anything more serious than a traffic violation, basically). If a person is imprisoned for a crime, they are excommunicated, automatically, and must be re-baptised once they are released from prison. LDS missionaries who misbehave on their mission are frequently dealt with quite sternly for their miscreance.
Perhaps my comments were a bit disrespectful to Catholics; my deepest apologies. At least Catholics could reasonably expect SOME SORT of repercussions from their Church. In many Protestant churches, any consequences would likely come exclusively from civil authority, though some of the stricter Evangelical or fundamentalist churches might take stronger measures. With all due respect to Roman Catholics however: even a convicted murderer about to be executed for his or her crime will be absolved of the sin of their act if only they make a good and valid confession. (Granted, the murderer would, upon execution, face a burdensome future in Purgatory, unless they managed to achieve a state of perfect contrition for their sin).
My comments–again, with no disrespect intended–were meant to contrast the degree to which LDS church-members can expect rather stern consequences from their church. I don’t think it is usually or customary for modern Roman Catholics to have penances imposed upon them that are anything like the penalties the LDS may expect. What the young men in this case will endure is difficult to say, and we may never be privy. But I have personally known of LDS who were penalized quite the way I have described, for miscreance that was much less serious and certainly much less public than what these young men have done.