There was only the books of Moses translated into Greek before Christ - not the whole OT. This is documented by various sources. Origen's Hexapla is the first/oldest copy of the "Septuagint" in existence that contained the whole OT - and many believe that he was the one who translated it himself.

Alfred Edersheim mentions this in his book The Life And Times Of Jesus The Messiah over 100 years ago. I think Josephus also mentioned the Pentateuch in Greek, though no mention of the rest of the OT.