This is a controversial one, as the question of the death penalty for Christians, has been long debated, so we can expect that we may respond to this story in different ways. The Pope has revised the Catechism, to now condemn the death penalty: 
  http://www.catholicnews.com/services/englishnews/2018/pope-revises-catechism-to-say-death-penalty-is-inadmissible.cfm  
  https://www.independent.co.uk/news/world/americas/pope-francis-death-penalty-catechism-capital-punishment-trump-executions-catholic-church-vatican-a8475026.html

“Building on the development of Catholic Church teaching against capital punishment, Pope Francis has ordered a revision of the Catechism of the Catholic Church to assert "the death penalty is inadmissible because it is an attack on the inviolability and dignity of the person" and to commit the church to working toward its abolition worldwide. The catechism's paragraph on capital punishment, 2267, already had been updated by St. John Paul II in 1997 to strengthen its skepticism about the need to use the death penalty in the modern world and, particularly, to affirm the importance of protecting all human life. Announcing the change Aug. 2, Cardinal Luis Ladaria, prefect of the Congregation for the Doctrine of the Faith, said, "The new text, following in the footsteps of the teaching of John Paul II in 'Evangelium Vitae,' affirms that ending the life of a criminal as punishment for a crime is inadmissible because it attacks the dignity of the person, a dignity that is not lost even after having committed the most serious crimes."

"Evangelium Vitae" ("The Gospel of Life") was St. John Paul's 1995 encyclical on the dignity and sacredness of all human life. The encyclical led to an updating of the Catechism of the Catholic Church, which he originally promulgated in 1992 and which recognized "the right and duty of legitimate public authority to punish malefactors by means of penalties commensurate with the gravity of the crime, not excluding, in cases of extreme gravity, the death penalty." At the same time, the original version of the catechism still urged the use of "bloodless means" when possible to punish criminals and protect citizens. The catechism now will read: "Recourse to the death penalty on the part of legitimate authority, following a fair trial, was long considered an appropriate response to the gravity of certain crimes and an acceptable, albeit extreme, means of safeguarding the common good.

"Today, however, there is an increasing awareness that the dignity of the person is not lost even after the commission of very serious crimes. In addition, a new understanding has emerged of the significance of penal sanctions imposed by the state. Lastly, more effective systems of detention have been developed, which ensure the due protection of citizens but, at the same time, do not definitively deprive the guilty of the possibility of redemption," the new section continues. Pope Francis' change to the text concludes: "Consequently, the church teaches, in the light of the Gospel, that 'the death penalty is inadmissible because it is an attack on the inviolability and dignity of the person,' and she works with determination for its abolition worldwide."

     Now, there are merits in the Pope’s argument, but other Christian theolgicians, even in the Catholic tradition have taken an opposing view; this is a historical fact that one can look up:
  http://theconversation.com/is-the-death-penalty-un-christian-76687
  http://religion.blogs.cnn.com/2014/05/01/why-christians-should-support-the-death-penalty/

     On this one, I tend to the position that the death penalty is problematic, but I don’t hold to this dogmatically. Society definitely deserves protection from those who would do the most horrendous of things. Yet, I cannot escape the feeling that the Pope is probably championing this case in opposition to the US, and Trump who wants to go hard on ruthless killers, especially the illegals. The pc lobby, naturally defends gangs like Mexico’s MS-13, which is sending more of its violent young to the US:
  https://www.youtube.com/watch?v=a0_U9jSJ41A 
  https://www.youtube.com/watch?v=WD-g7f0Eoo8

     The level of violence of this gang cannot be matched in the modern era of crime:
  https://www.telegraph.co.uk/news/2017/11/23/ms-13-gang-beheaded-tore-heart-man-near-washington-park/

     Remember, if the most violent are not executed, then if social breakdown occurs, the prisons may empty, or if the libtards pursue their full agenda, they will empty prisons, so that kind gentle folk in the green leafy suburbs may have to face home invasions that they are too weak to cope with.