Mukhthiar Ahmed Khudabakhsh, the father of the 4-year-old victim, says the sentence was carried out on Thursday at a shooting range in Dubai.
The boy's parents were among five family members present for the execution of Rashid Rabee al-Rashidi, a 30-year-old boat captain convicted of raping and killing the boy Moosa in a mosque bathroom in November 2009.
The UAE's last execution was in February 2008.
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