Prisons have iron bar gates that cannot be broken or shot out by some lunatic. Visitors are buzzed in and buzzed out from a secure waiting room where anybodys reason is checked out for being a visitor. Something more radical has to be done for safety when so many more people are mentally unstable.
... and weapons and drugs still are smuggled into prisons. When society has gone morally soft on the inside, no amount of physical hardening on the outside will save it.