A security question is a common safeguard many websites take in order to enable a user to still access their account even if they forget their username and/or password. The thinking behind this practice is that the questions asked are extremely personal, and therefore should only be answerable by the account owner. In this case, the person setting up the account has presumably committed a crime involving the disposal of bodies and the police are trying to catch him by planting a security question on an email account creation system. Their hope is that the suspect will think nothing of the questions since they are so common when setting up email accounts and that he’ll fill it out with the location of the bodies. The suspect begins to type out the location, but he catches himself and realizes it’s a trap, thwarting the plan of the police.
