"The inmate said he had nothing planned. He just wanted to make sure he didn't lose it," Canterbury said.
The gun was found by another guard who noticed Grantham looked like he was trying to hide something in a blanket, he said.
Because of the foul-up, guards are now using hand-held metal detectors during searches, he said.
Until now, jail officials had thought it unnecessary because police officers usually find any weapons. Only visitors had to go through metal detectors, he said.
The jail was busy with drunken driving arrests the morning Grantham was brought in by two police officers, Canterbury said.
Grantham was searched once and put into a holding cell, where he stripped and hid the gun, he said.
After Grantham showered and put on a jail uniform, the same guard made a second mistake by putting Grantham back in the same cell. That went against regular policy, he said.
A second guard then searched Grantham and didn't find the gun, he said.
The location of the booking area is not ideal because it is close to the lobby, where there is potential for more confusion, he said.
That flaw will be corrected in the design of a new regional jail to be built in several years, he said.
"There were a few extenuating circumstances, but not enough to excuse these lapses," he said.
The guards, whose names were not released, will be suspended for five days and have letters of reprimand placed in their files. They had no previous infractions, he said.