"The original owner is deceased"

When, relative to this sale?

"the children of owner inherited the building"

Did they? Or, did the person who owned the building die, and this building is part of the estate of the deceased, and once the building is sold, the Funds are then part of the estate, and the funds are dispersed?

Or, the children really did inherit the building (in which case, when, relative to the death)/ And they own a building and all have agreed it should be sold and all will get their share of the proceeds?

You are not giving any perspective to the sequence of events. You seem focused on the distribution of Funds, but no one can answer until you help determine what happened and when and it what sequence, for purposes of tax reporting.

Here is an Example of how to tell the story to us:

The person died last week leaving a home that was wholly owned and had three adult children that will inherit the home and any remainder of the estate through a will. The building is considered to be part of the deceased estate that totals about $1million, so the sale, which is timely and at FMV, might mean that nothing will be reported on the tax returns. The inheritance is no longer "share of building" but "share of proceeds" with no gain to report.

Or, the children inherited the commercial building a few years ago, and now they have decided to sell that building.

See how the story matters?