It’s never a good idea to have an armed officer handling inmates in transit. It’s best to have an unarmed officer handle the inmate while the armed officer remains a short distance away. It’s too easy for an inmate to grab the gun if the officer is busy hooking them up.
And why most jails/prisons the guards are unarmed when they're dealing directly with inmates. But the fact remains, even cops on the streets transport violent felons all the time while armed. Bottom line is, if they're going to put obvious weak links in the chain, they should expect that chain to be broken on occasion.