Dutch Boyd Eliminated ... a chop? what?

[HentaiGaijin]

Dutch Boyd Eliminated
Log: Dutch Boyd is all-in preflop with K-10 and is called by Chris Todlewski with A-A. The board comes Q-J-5, giving Boyd an open ended straight draw. The turn is a K. Boyd can now also hit an A for a chop. The river is the 4s, and Dutch Boyd's busted straight is eliminated by Todlewski's pocket Aces. [Source: Cardplayer.com]

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K10 v AA, on QJ5K

How does an A on the river result in a chop?