After the pictures emerged, several people took to Twitter to voice their outrage and suggest that the royal family should have been more mindful about the toys they give Prince George and Princess Charlotte.
The duchess proved her savvy shopping skills yet again today, stepping out in a relatively cheap Zara dress alongside Prince George and Princess Charlotte to watch Prince William compete for the Maserati Royal Charity Polo Trophy.
Prince George wore a navy blue polo shirt with Khaki shorts while his sister Charlotte wore a pink floral frock. I really don't get toy guns - why play with things you should never have to use.
The next day, George, 4, and Savannah, 7, showed again that they are definitely a playful pair of cousins, as they enjoyed a day out at the Beaufort Polo Club in Gloucestershire.
The third-in-line to the throne was photographed playing with the gun with a friend in the grass.
She was also seen relaxing in Kate's lap and climbing up a bank with her mother. My American side here, biased maybe b/c of everyday #gunviolence in United States of America, but my British side agrees.
"Here's why the sight of #PrinceGeorge playing with a toy gun is triggering for some of us".
However, many also rushed to defend Prince George and his parents, pointing out that the young royal will one day be Commander-in-Chief of the British Armed Forces.
These worries primarily stem from how some toy guns are made to look just like real ones, creating a fear that if presented with a real gun, the child won't understand the danger in it. "Lucky George isn't black or police would have shot him", one user wrote.
Sunday's Polo match was the first of a series of charitable matches that Prince William and Prince Harry will take part in over the summer.