I hope that native speakers will give you their opinion but here's mine. Do you know that the foreigner we're talking about killed his son? (he killed his son but you may not know it; in my opinion "that" is not optional here) Do you know whether the foreigner we're talking about killed his son?
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
s081873 Btw, is there also any custom of releasing sky lanterns in your country, France?Not yet!!!
s081873(A) Do you know the foreigner we're talking about "killed" his son?
(B) Do you know the foreigner we're talking about "kills" his son?I assume the quotes are just to draw our attention to the crux of your question. Bold face would have been better because the quotes indicate a non-literal usage of the word, and the word "kill" is used non-literally quite oft