He was prone to exaggeration when trying to pick up women, claiming that he saved the Commander from a Tyranid during the mission to recover the generator.
Just as the Commander was about to start his/her speech in Rivet City he, Hawk and Kurosawa were caught in the blast by the Western chapter of the Brotherhood of Steel's gunship. He was the only one out of the three who managed to survive, due to being a short distance from the initial blast, which only launched him across the market. As he lay bleeding to death, the Commander spoke to him briefly and tried to save him, and the technically-minded Private cracked a little joke just before he expired.
When in comabt, Private Ruiz was armed with an XM-586 Assault Rifle.