يقال في عرف المجرمين وممتهني الإجرام إنه لم يزل بعض أطراف أو زيول (هكذا بالعامية ) للجريمة
ويطلق عليه رجال القانون (الخيط الرفيع)

when thugs kill someone after extracting information, that's because they don't want him to give this information to anyone else. Should they keep him alive, they risk being identified and persecuted, or they risk the same information going to their adversaries, and this, I think, is what they don't want to happen. So they are trying to avoid the undesired aftermath of not killing the man, which could be translated into Arabic to: لتفادي ما قد لا تحمد عقباه، لتفادي نتائج غير محسوبة
especially that one of the meaning of loose end is: Confusion
http://www.macmillandictionary.com/dictionary/british/loose-...