A canonical response to a murderous priest
There are arguments under the current criminal law of the Church (Book VI of the 1983 Code) whereby a priest who, in a one-time act, sires a child with a consenting adult, could escape dismissal from the clerical state for the deed, notwithstanding the other penalties that might be imposed on him (a careful reading of CIC 18 and 1394-1395 demonstrates this). I don't know whether the facts in this case would have allowed such an argument to go forward; my hunch is, the odds are against it.
But in murdering the progeny of his misconduct, a priest renders any such arguments moot and makes his expulsion from ordained ministry a simple matter.
Canon 1397 states that anyone who commits homicide can be punished in accord with Canon 1336, a norm that in turn authorizes "dismissal from the clerical state" as a penalty for certain offenses. As if that weren't sufficient basis for dismissing a homicidal priest from the clerical state, a canonical judge is permitted to augment penalties on those who have been "established in some dignity" (CIC 1326).
Priesthood is surely such a dignity. It should be canonically vindicated against such dastardly conduct.