A huge pillar of flame that shot upward 'like a giant blowtorch,' in the vicinity of the mainmast, followed by an explosion that destroyed a large portion of the ship from amidships clear to the rear of "Y" turret, blowing both after turrets into the sea. The ship broke in two and the stern fell away and sank.
Hood had tunnels that connected the magazines to the turrets. It has been theorized that these tunnels propagated fire along the ship, which was lightly armored against plunging fire.
American Battleships had a tunnel called “Broadway” running from B turret barbette to Y turret barbette. It was there to facilitate the transfer of projos and powder bags between the two if needed. It ran under the armor deck.
People forget that the Prinz Eugen was also there and firing on Hood, but it was Bismark’s second salvo that straddled her, and her Bismark’s third salvo that blew her up. By contrast, Prince of Wales never engaged the enemy, but retired in a rain squall following Hood’s sinking.
In WW1 the Royal Navy had a bad habit of leaving the doors open between the magazines and the turrets so that ammunition could be moved faster. This was in violation of their own safety standards and due to this the Brits recklessly lost a lot of ships at Jutland.
I recall reading that same practice being considered as a reason for the demise of Hood.
The US and Japanese navies in that same time required all the doors between turrets and magazines to be closed immediately before and after ammunition passed through them and that practice saved lives in both navies.
That was the nature of battle cruisers - trade armor for speed.
Of course, the numbers start looking a bit different when you compare the Hood to a roughly contemporary US battleship such as the Arizona. Hood is larger, they are roughly the same speed, Hood has larger guns (15" compared to 14") but the Hood deck armor ranged from three quarters of an inch to 3 inches, while the Arizona had 5". Of course, the survival of each in combat can be measured in minutes.
In my travels, I've had occasion to witness the powder in a U.S. 120 mm. tank round poured on the ground and set alight. Maybe 15 lbs. total.
It was most impressive.
I can't imagine 10's of thousands of pounds of propellant firing off at the same time.
Rest assured that anyone in the area suffered for only a very short time.