Moses, therefore, described them to Pharaoh as such. The plague, however, struck at night. At night, these people were incarcerated in order to prevent their escape. Hashem did not punish them out of malice. Rather, this slaying was meant as a stern lesson.
People are only human, and as such, are prone to error.
Unfortunately, we tend to project our humanity upon Hashem, too. Consequently, when things go awry, we are inclined to attribute our failure to a deficiency in Hashem, rather than admit our own fallibility. No person is perfect. If we can admit to ourselves that we are not infallible, we might find that we can better deal with the faults of those around us and those we find within ourselves. Please pass it on to a friend.