Hi David,
There is an account of Private Hollands death in "The History of the XIIIth Hussars" by C.R.B. Barrett in 1911:
The attack on Langzeekoegat (29 April 1901):
"On the following day the mobile column marched from Uitkyk at 4 A.M. to attack the laager of Hans Botha at Langzeekoegat.
A Squadron was in advance, with the Johannesburg Mounted Rifles and guns in support. For an hour there was a thick fog which then lifted slightly, and Lieutenant Stern, who was with the leading troop, sent out a section as far in advance as the mist would permit with safety.
Half an hour later Guide Ward, who had been with this section, galloped back to say that they were just on the laager.
Unfortunately, just at this time the fog became thicker, nevertheless the leading section (Corporal Cave) on coming on the Boers' outpost charged them, and Lieutenant Stern's troop rushed the laager.
For some reason it appears that at this time the rifles were carried slung on the off side, and in consequence the use of the sword was by no means facilitated; hence this charge was not so effective as it might have been had the rifles been slung on the near side, as they were subsequently.
The supporting troops, who could not fire, as friends and foes were alike invisible, or if seen indistinguishable, were stopped by wire. The Boers got off, though they left four prisoners behind, besides all their waggons, blankets, food, &C., and many saddles.
One man, Private Mills, was shot through the heart as he galloped into the laager, Private Hayes and Private Basden being mortally wounded at the same time.
Lance-Corporal House received a slight wound through the thigh, and had eight bullets in his horse.
Four horses were killed, of which one belonging to Lieutenant Stern was hit in five places. Besides these, six horses were wounded.
Later in the day, during the retirement to camp,
Private Holland, who was one of the rear-guard, was most unfortunately killed by one of our own shells. It was undoubtedly due to the fog that the enemy
did not receive far greater punishment."
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It appears as if Private Holland wasn't wounded a few days before Langzeekoegat but was killed by friendly fire on the day itself (29 April).
It appears as if the attack on Langzeekoegat was the deadliest day of the war for the 13th Hussars; from the same book referenced above: