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Board Certified Physicians
Meet Our Doctors
Dr. John Rayfield
John Rayfield, MD is a staff physician at the Schertz/Cibolo Emergency Clinic. He is Board Certified in Emergency Medicine and has 20 years of experience as a doctor.
Dr Rayfield retired from the Army as a Lieutenant Colonel in 2013 after 20 years of service. He enjoyed operational medicine and spent the majority of his career assigned to troop units. He has almost 3 years of combat time in Iraq and Afghanistan serving with the 24th Infantry Division, 1st Cavalry Division and US Special Operations Command in addition to a tour as a United Nations Peacekeeper in Macedonia while assigned to the 1st Armored Division. One of the many highlights of his career was being the recipient of the Spurgeon Neel Award, given annually to the top US Army Flight Surgeon for 2004. The latter part of his career was devoted to teaching and his last assignment was at the San Antonio Military Medical Center (SAMMC) as one of the Program Directors for the Emergency Medicine residency.
Dr Rayfield graduated from the United States Military Academy at West Point, then earned his medical degree from the Uniformed Services University of the Health Sciences in Bethesda, Maryland. He completed internship and Emergency Medicine residency training at SAMMC, serving as a Chief Resident during his senior year.
It is a pleasure to be part of an outstanding group of healthcare professionals here in Schertz and looking forward to being of service to the community.
Robert M. Gonzalez, MD
Dr Gonzalez is a Board Certified, residency trained, Emergency Medicine Physician. He brings 20 years of Emergency Medicine experience to the Schertz-Cibolo Emergency Clinic. He completed his undergraduate degree at Abilene Christian University; medical school at the University of Illinois College of Medicine; and his Emergency Medicine specialty training at Maricopa Medical Center, a level one trauma and regional burn center in Phoenix, AZ. He began his practice in San Antonio, TX in 1997 with the Baptist Health system. In 2006 he transferred to the Seton Health System in Austin, TX; where in addition to his clinical duties as an attending physician in the ER, he served as Chief of Staff at Seton Southwest Hospital..The Gonzalez family has a special connection with Schertz-Cibolo area, as their son graduated from Samuel Clemens High School. They reside in the Garden Ridge area where they dabble in their favorite hobbies which are beekeeping and dog sport. He and his wife, Nancy, are very happy to be back, closer to family and friends.
Dr. Ricardo Castillo is one of Schertz Cibolo Emergency Clinic’s physicians, who was born and raised in Brownsville, Texas. Dr. Castillo graduated from the University of Texas at San Antonio with an undergraduate degree in Biology. He earned his medical degree from the Texas College of Osteopathic in Fort Worth, Texas. Dr. Castillo subsequently did his Family Practice Residency at Scott and White Hospital in Temple, Texas. He is currently Board Certified in Family Medicine.
Dr. Castillo has done extensive work in emergency medicine and urgent care clinics throughout his career. He is actively involved in helping to prepare future practitioners with the University of Texas Health Science Center’s Family Practice Preceptor program. He also enjoys being an Assistant Clinical Professor at the University of the Incarnate Word’s School of Osteopathic Medicine.
Dr. Castillo and his wife have three children. He loves all outdoor activities, traveling, and sporting events.
William Gibson MD
Dr. Gibson is residency trained in Emergency Medicine and Pediatrics. He is board certified by the American Board of Emergency Medicine. Dr. Gibson is an honorably retired officer for the United States Air Force having spent over 23 years active duty. While a member of the military, Dr. Gibson served as a Flight Surgeon as well as pediatrician and emergency medicine physician with numerous deployments and significant leadership positions. These include the Associate Program Director for the San Antonio Joint Air Force and Army Emergency Medicine Residency program at Brooke Army Medical Center. After his retirement, he served as Assistant Professor and Pediatric Emergency Medicine Consultant at the University of Texas Health Science Center in San Antonio. Dr. Gibson is the author of multiple publications in the medical literature. He has also given local, regional and national lectures including to the national meeting of the Society of Academic Emergency Medicine. Dr. Gibson is married with two adult children. His daughter is a world-class swimmer who represented the United States at the 2017 World Aquatics Championships. Her accolades include being named to the NCAA Today’s Top Ten Athlete Scholars in 2018. His son is both a student and a leader of the Georgia Institute of Technology Robojackets team which competes nationally in robotics competitions. Honorably Discharged from USAF effective 1 July 2006
Dr William Friedrich is a staff physician at Schertz Cibolo Emergency Clinic. He brings 25 years of experience to the emergency department.
Born in Houston, he received his Bachelor of Arts degree in Chemistry at Texas Lutheran College in Seguin. In 1993, he earned his Doctor of Osteopathy from Texas College of Osteopathic Medicine in Fort Worth. He completed his internship at the Osteopathic Medical Center of Texas. He moved to San Antonio in 1994 for residency training at the University of Texas Health Science Center San Antonio department of Family and Community Medicine. He has been Board Certified by the American Board of Family Medicine for the past 24 years. He has enjoyed work as attending emergency room physician in county emergency departments including Wilson, Atascosa, Uvalde, and Medina. And for the past 8 years has attended at local micro hospitals in the San Antonio area.
Dr Friedrich and his wife Cindy, a San Antonio native, enjoy travel and spending time with their four children.
“I believe in treating my patients the way a loved one or family member would like to be treated."