The decedent did not actually or constructively receive the cash from the sale until after death, therefore it definitely goes on the 1041. (Just like if he requested his RMD before death but the check didn't arrive until after.)
The real question is whether it is IRD or income to the estate. This makes a difference because basis will be different.
Pubs aren't "authority," but Pub 550 mirrors the code: " Securities traded on an established market. For securities traded on an established securities market, your holding period begins the day after the trade date you bought the securities, and ends on the trade date you sold them." In your case, the trade date occurred after death, so I would say the estate sold them and gets stepped-up basis. (The estate comes into existence at the moment of death, so there is no way the decedent could have sold the stock.)
Now the fun part of determining basis. Since the person died on a Saturday, which is not a trading day, you get to do some fancy math. First find the high and low prices of the stock on Friday and average them. Do the same for Monday's prices. There are three days between Friday and Monday, so you have to weight the averages: (Friday's mean X 1) + (Monday's mean X 2)/3. There is your basis.
Note that the broker will give the decedent a 1099, so you'll have to report the sale on the final 1040 and back it out. Have fun, and do charge A LOT.