From the Wikipedia page 
Sir James Tyrrell (c. 1450 – 6 May 1502) was an English knight, a trusted servant of King Richard III of England. He is known for confessing to the murders of the Princes in the Tower under Richard's orders. However, his statement may have been taken under torture, so the confession might not be genuine. William Shakespeare in his play Richard III portrays Tyrrell as the man who organises the princes' murderer.
Tyrrell was the eldest son of Sir William Tyrrell (c. 1415 – 22 February 1461) and Margaret Darcy (c. 1425), married in 1444. Like his father before him, a loyal Yorkist, James was knighted in 1471.
He married Anne Arundell on 9 March 1483. They would later have a son also named James Tyrrell. After Richard III assumed power, he was appointed High Sheriff of Cornwall in 1484.
James was in France in 1485 and played no part in the Battle of Bosworth Field which signalled the end of the Yorkists and the start of the Tudor dynasty.
In the following year, he returned to England and was pardoned by King Henry VII, who reappointed him governor of Guisnes (in the English possession of Calais). However, in 1501, Tyrrell lent his support to Edmund de la Pole, 3rd Duke of Suffolk, now the leading Yorkist claimant to the English throne, who was in voluntary exile. When Henry heard of this, Tyrrell was recalled, accused of treason, and tortured.
Thomas More wrote that, during his examination, Tyrrell made his confession as to the murders of King Edward V of England and his brother Richard of Shrewsbury, 1st Duke of York. He also implicated two other men; despite further questioning, however, he was unable to say where the bodies were, claiming that they had been moved. He was beheaded at Tower Hill on 6 May 1502, together with one of his accomplices in aiding Suffolk, Sir John Wyndham.