It is inarguable that had the murderer, Usman Khan, still been in jail this would not have happened. Yet this terrible incident should not be turned into a political football, even though we are in the midst of an election campaign.
Regrettably, this is already happening. Boris Johnson has blamed the previous Labour Government for early-release policies that allowed the killer out, and the Opposition is returning fire with claims that underfunding of the prisons system is creating an atmosphere in which mistakes are made.
Such party political squabbling at this point is unedifying and not helpful.
The inquiry into what happened, and the background to it, must be allowed to run its course before any definitive judgements are reached.
It will need to examine all the circumstances, including broader questions about the rehabilitation of offenders in prison and how effectively that is monitored.
In this instance, it initially appears that the murderer had somehow managed to dupe the authorities into wrongly believing he was a reformed character.
The Prime Minister is right to have ordered a review of the licensing conditions on 74 other convicted terrorists who have been released from jail. Public protection demands that everything possible is done to identify risks and prevent further attacks.
But political rhetoric on all sides needs to be toned down.
What is required now is a thorough and easured assessment of the risks to society, sentencing policy and the work taking place within prisons to deradicalise terrorists. Whatever conclusions are reached should then be supported by all parties.