Charles Spurgeon Commentary Acts 16:27

"And the jailor, being roused out of sleep and seeing the prison doors open, drew his sword and was about to kill himself, supposing that the prisoners had escaped." — Acts 16:27 (ASV)

For the law was that, if a jailer lost a prisoner, he was to suffer whatever penalty the prisoner would have suffered. He therefore knew that, in all probability, his own life would be taken; and, strange to say, to save his life he would kill himself.

Suicide is ever absurd and unreasonable. The worst that could happen to him would be to die by the sword of justice; and to escape from that, he tries to die by the sword of a suicide.