Assalamu alaikum. Recently one of the western dai's has shared a story on his facebook page from Ibn Al-Jawzi in AlMuntatham fi Siyar AlMuluk wal Umam. In that story, Abdullah ibn AlMubarak met a boy who asked to Allah something and at that instant his du'a would be accepted & came to reality. When that boy found out that his secret with Allah has been revealed to Abdullah ibn AlMubarak, he asked for his death and at that instant he was dead. My question is, is this story authentic? Jazak-Allahu khairan.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

We did not find the story which you referred to in the question. Knowing whether or not this story is authentic will not lead to doing certain deeds or not doing them. A believer should have certainty that Allaah answers the supplication (of His slaves). On the other hand, supplicating for death or other calamities is forbidden in principle as in the Hadeeth which reads: "Do not invoke curses on yourself or on your children or on your servants or on your wealth." [Abu Daawood]