Luke does not explain how Paul knew that the jailer was about to kill himself or that the prisoners had not escaped. Speculation at this point is of no value to the translator.
Quoted with permission from Newman, Barclay M. and Nida, Eugene A. A Handbook on The Acts of the Apostles. (UBS Handbook Series). New York: UBS, 1972. For this and other handbooks for translators see here .