>>17802922 (OP)
Devil's advocate:
Someone who repents has to genuinly mean it and there is no chance in hell a random person who decided on the short term to kill people for fun has any chance to feel the weight of his sins.
But theoretically it is possible, but a person who murders on his whim only to repent immideatly afterwards doesn't get born very often.
It also depends on the sect of Christianity. Catholics and Lutherean Evangelicd believe in this, but some smaller sects do not believe in repetentance for such sinful acts.