Lopez's parents, Cayetano and Candida immigrated to Mission, Texas from the Mexican city of Oaxaca. His father worked on the cotton and beet fields of Mission for sometime, however he returned to Mexico and perished in the Mexican Revolution. Lopez was raised by his maternal uncle after his mother died when he was eight years old.
While living in Brownsville, Texas, with his uncle's family, Lopez never attended school, instead he went to work in the cotton fields. As a young man, Lopez caught the attention of a boxing promoter and for seven years he fought a total of 55 fights the lightweight division. In 1934, during a boxing match in Melbourne, Australia, he met a group of Merchant Marines and signed a contract with them. He was accepted in the union in 1936 and spent the next five years traveling the world.
He was en route to California from Hawaii on December 7, 1941, when he learned about the Japanese attack on Pearl Harbor. When he arrived in Los Angeles, the authorities believed he was Japanese and he was forced to prove otherwise.
Lopez returned to Brownsville and, in 1942, married Emilia Herrera. That same year, he received his draft card and went to San Antonio where he enlisted in the U.S. Army. Lopez was first sent to Fort Sam Houston, Texas, and then to Camp Roberts, California, where he received his basic training.
Lopez was awarded the United States' highest military decoration for valor in combat, the Medal of Honor, for his heroic actions during the Battle of the Bulge, in which he single-handedly repulsed a German infantry attack, killing at least 100 enemy troops.
Lopez received an enthusiastic reception when his ship landed in New York City and he was greeted by New York Mayor Fiorello LaGuardia. On a visit to Mexico City, he was greeted by the president of Mexico, Manuel Avila Camacho and awarded Mexico's highest military commendation, la Condecoracion del Merito Militar.
Even though he was a military hero, he was unable to get a good job in Brownsville and therefore moved with his family to San Antonio, where he was hired as a contact representative with the Veterans Administration. Upon the outbreak of the Korean War, Lopez volunteered to serve. President Harry S. Truman, ordered him returned home.
Lopez lived in San Antonio with his wife Emilia, at his daughter, Maggie Wickwire's home.
On his own initiative, he carried his heavy machine gun from Company K's right flank to its left, in order to protect the flank which was in danger of being overrun by advancing enemy infantry supported by tanks. Occupying a shallow hole offering no protection from the waist upward, he cut down a group of 10 Germans. Ignoring enemy fire from an advancing tank, he held his position and cut down 25 more Germans attemtping to turn on his flank. Glancing to his right, he saw a large number of infantry swarming in from the front. Although dazed and shaken from the enemy artillery fire which had crashed into the ground only a few yards away, he realized that his position would soon be outflanked. Again, alone, he carried his machine gun to a higher position to the right rear of the sector. Enemy tanks and infantry were forcing a withdrawal. Blown over backwards by the concussion of enemy fire, he immediately reset his gun and continued his fire. Single handedly he held off the German horde until he was satisfied his company had effected its retirement. Again he loaded his gun on his back and in a hail of small arms fire he ran to a point where a few of his comrads were attempting to set up another defense against the onrushing enemy. He fired from his position until his ammunition was exhausted. Still carrying his gun, he fell back with his small group to Krinkelt. Sergeant Lopez's intrepidity and gallentry, on seemingly suicidal missions in which he killed at least 100 of the enemy, were almost solely responsible for allowing Company K to avoid being enveloped, to withdraw successfully and to give other forces coming up in support time to build a line of defense which repelled the enemy drive.
