Assuming he worked for a company with a "no guns" policy, and he chose to carry a gun into work, and somebody noticed so he got fired for breaking a company policy . . . color me surprised.

If you'll get fired for fucking Sally in accounting, or cursing at customers, or taking the company laptop home so your kids can do their homework . . don't do those things. Unless Sally's worth it. Your call, I never saw Sally, maybe she's a doozie.

I'd stretch a policy and keep a gun in my car in the company lot, and if the company demands to search my car or I'll be fired, I'll refuse consent, and be fired for "refusing to allow them to search my vehicle without cause". Sounds better than "he brought a gun into work and we had to fire him once the screaming of the Woke women died down".

Work someplace else, if you can't tolerate the policies. I'd never work for Ben & Jerry's, or Bank of America, because they're commie assholes and I'm sure I'd hate their workplace cult.