Even the latest translations, in which the best tools for the work have been available, the mystery of this verse has not been cleared. The range of reasons for the killing is wide. Any one can be right, or all can be wrong. Even the experts in Bible scholarship do not agree. The number fifty creates a problem.
Seventy does appear to be a more reasonable number.
Although the writer may have been inspired to write, something drastic has happened to his words over time. A person who relies on one version only will consider that version to be right, even though there may be errors of translation, and also be unaware that there are other possibilities. A person who uses several versions will be aware of the inconsistencies. The latter person can weigh the possibilities and seek divine guidance if he is searching the truth. The same procedure is necessary throughout the Bible in order to glean the truth which it contains and eliminate the errors of copyists and translators.