Upvote:2
张作霖只说了一个“打”字,就昏死过去,再也没有醒来……。
"打" could be the verb in a sentence. That means 'make a phone/telegraph to call his fifth son back soon'. Because he was in a lethal condition and could not finish the whole sentence. This matches the following return of Xueliang Zhang disguised as a wound soldier.