Interview with a silent (undercover) agent

How did you get on the track of the thief?
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Were you suspecting him wor a long time already?
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Were you already on his track before he tried to leave the country?
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Did he betray himself? And - if yes, how?
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Do these kind of things occur frequently?
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Do you want to amplify this interview with a last statement?
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Thank you.
....(nodding: welcome).