Bamboo is a grass. It'll come back. What has turned brown is already dead. It's OK to cut it back so long that you don't cut the shoots.

Any culms that were brown/tan could have been pruned out, by cutting them back to the ground, not to 3 feet. Culms that were still green should have been left alone to give them a chance to re-leaf. Bamboo is not like many other plants: a living culm does not get stimulated to put out new growth after a pruning (shall I call it an amputation?).

Whatever tools your husband used to butcher the bamboo should be hidden from him as he does not know what he is doing.

If you have new shoots coming up, the roots are not dead. It may take a couple of years to recover, but you didn't lose it.

The stems that turned brown ARE dead, and should be pruned off at ground level, not 3 feet up ... send him back out to finish the job before the new shoots get going and make it really hard to finish.

Here in OKC, my running bamboo looked totally brown after this winter, but in reality, the stalks themselves (called culms) were mostly green, but all the leaves were brown. We did have some brown culms, too. After plentiful rainfall the last few weeks, almost all the bamboo is green again (between the green culms leafing out and the new growth from the base of the plant just in front of the main grove). The culms that are totally brown, stem and all, we've been working to break off/cut at the ground level and remove. This is something we do periodically anyway, because the culms only live so long and need to be removed so the grove stays healthy.

Since you are one zone colder than me, yours might have truly been all brown, stems (culms) and all. And even though your husband cut it down, my experience with our established bamboo over the last few years is that it will be back if it's a running variety! :) We'd completely clear cut a 6x6 foot patch to install a new fence last October, and now, you'd never know it had been cleared.

What you write is all correct. Anything that is live will re-leaf, whether it's pruned or not. It's just that having 3' tall stubs -- whether they are dead or alive -- looks terrible.