he did
He did it in his free time.
Er wusste ganz genau, was er tat.
He knew exactly what he was doing.
Er wusste, dass keinen Sinn hatte, was er tat, aber so lautete der Befehl.
He knew that what he was doing made no sense, but that was the order.
Tom wusste, dass das, was er tat, falsch war.
Tom knew what he was doing was wrong.
I know what he did.
Er tat Zitronensaft in seinen Tee.
He put lemon juice in his tea.