Summary
Noncommissioned officer in the UNSC Marine Corps and a member of the Orbital Drop Shock Troopers. Sergeant Parker was stationed aboard the Pillar of Autumn as part of the ODST detatchment under First Lieutenant Melissa McKay.
Like most of his commrades, Sergeant Parker abandoned the Autumn when it was attacked by the Covenant over Installation 04 using a Human Entry Vehicle to "Helljump" to the surface of the installation. He then assisted in the attack on the mesa that would be Alpha Base.
Later, he led the ODST attatchment that accompanied the Master Chief on the mission to rescue Captain Keyes, who was captured aboard the Truth and Reconciliation. Parker was tough and led his men well. After the drop off from Pelican Echo 419, Parker and his ODSTs were very helpful to the Chief, but he felt that they slowed him down because they did not have the reflexes and combat skill other Spartans had.
Parker was wounded by the spines of a Hunter in the cargo bay. Nevertheless, he shrugged it off and continued to lead the attack, liberating Keyes from the prisons of the vessel.
He is assumed killed either in the Covenant attack on Alpha Base or in the destruction of the Truth and Reconciliation when the ODSTs returned to it.
His/Her gender however, is unknown because he/she is refered to as both a man AND a woman. It is assumed he is a man, as there are many references to him/her being a man, and only one saying he/she is a woman. See: List of Inconsistencies in Halo