Half measures will be the death of this country, if it is indeed still salvageable and I believe it is. Any rational society would either put these people to death or at least implement punishments strong enough to discourage similar behavior in the future.
Society is built on trust, common beliefs and justice. In the absence of the first two, equal justice under the law can somewhat keep it afloat.
Absent the rule of law, eventually things devolve in one of two ways. Either by people taking things into their own hands or by those in control eventually taking away any means to do so and therefore complete subjugation.