The Cornerstone Team

Everyone on staff at Cornerstone Healing Center is living a life free from active addiction. We’ve helped hundreds of people find long-term, meaningful sobriety — and we can help you, too. But you have to take the next step.

Estil Wallace, Founder/CEO.  Estil has worked in the recovery field for 12 years. He has served 5A.org as the organization’s’ Executive Director, Board Member and President. Estil has also worked directly with alcoholics and drug addicts inside of the Maricopa County jail system including Tent City, Lower buckeye, Durango and Towers Jail. Additionally, Estil has over 14 years of experience with inside/outside sales, management, networking and digital marketing. He believes that anyone can heal that has the willingness to change.

Marcus Clark, Executive Director/COO. Marcus has worked in the Mental Health / Substance Abuse field for over 5 years. Marcus specializes in developing and managing substance abuse and mental health programs. He has worked with Phoenix Fire and Police Departments developing processes for training, managing, community involvement and coordination between various mental health organizations. He has also worked with Pinnacle Peak Recovery, Scottsdale Providence Recovery Center, as well as three different mental health disorder programs for Community Bridges and Empact SPC.

Dr. Stacey Smith PhD, Chief Clinical Officer. Stacey is a licensed psychologist in both Arizona and Texas and has been working in the addictions field in residential and IOP settings since 2010. He has a wide variety of experience in the addiction field, including work with individuals who suffer from addictions to alcohol, drugs, intimacy/relationships, sex, and gaming addictions.  Early in his career, Dr. Smith trained in EMDR techniques, knowing the important role that trauma work plays in the recovery process. Most recently, examination of how the brain works and how technology can play a key role in client recovery has been a focus of his work.

Karen Williams, Clinical Director.  Karen is a Licensed Professional Counselor specializing in Addiction Recovery, EMDR and Family Systems Theory at Cornerstone Healing Center in Scottsdale, AZ.  She holds a Master’s Degree in Professional Counseling from Grand Canyon University and has nearly 15 years of experience in substance use recovery, and the behavioral sciences.  


Dr. Paul G. Flatley

Medical Director

Dr. Paul G. Flatley D.O. FACEP has practiced medicine for over 20 years and is board certified in Emergency Medicine by the American Board of Emergency Medicine. Dr. Flatley is a member of the American College of Emergency Physicians. He has served as the Medical Director for the Emergency Department at Scottsdale Healthcare and is also currently the Team Emergency Physician of the Arizona Coyotes and volunteer at ChristCares Clinic in Phoenix, AZ.

Dr. Cassandra Sankey Scottsdale Cornerstone Healing Center

Dr. Cassandra Sankey

Occupational Therpist

Dr. Cassandra Sankey, OTD, OTR/L, specializes in mental health, sensory processing, and substance use treatment, at Cornerstone Healing Center, in Scottsdale, AZ. She completed her Doctorate in Occupational Therapy from A.T. Still University focusing on community reintegration programming for the Arizona Department of Corrections, Maricopa Reentry Center. 

Paula Brungardt, Cornerstone Healing Center

Dr. Paula Brungardt

Nurse Practitioner

Dr. Brungardt FNP earned her Doctor of Nursing Practice from the University of Nebraska Medical Center and specializes in Family Practice. She is currently attaining her Psychiatric Mental Health Endorsement from Maryville University. Her passion is in overall mental and behavioral wellness.  Her practice includes all age groups, helping pediatric and adult patients with mental, behavioral, and addiction issues. She has a full scope of practice and takes a holistic approach to health care; mind, body, and spirit.  She is also certified to provide Medication-Assisted Treatment psychopharmacology for addiction treatment.

Charlene is currently working towards her licensure as a LPC. She also adds 18+ years of sobriety to our team. Her dedication to helping others has been the primary focus of her recovery. By addressing life skills, while utilizing recovery tools, she maximizes on the strengths of our clients to reach their full potential and achieves results by her direct approach. Her interests outside of recovery include hiking, tennis, meditation and time with family and friends.

Lionel Estrada has been working to help those struggling with substance abuse for over three years starting at Crossroads for men, Community Bridges, and Community Medical Services before landing his dream job as a therapist at Cornerstone. While staying true to his own recovery program, Lionel is currently working on his Masters in Addiction Counseling.

Paige Warren, Director of Billing. Paige has worked in the mental health and substance abuse field for over two years, after starting as a Behavioral health technician, she then started her career specializing in insurance and billing. Paige also brings over 4 years of sobriety to the team. She hopes that she can use her experience to help others suffering from substance abuse. 

Scott Brunst, Director of Business Development. Scott specializes in program development/management. He and his team built Community Bridges Inc’s The Chronic Recitivator Navigator Program, The Community Comprehensive Health Program, City of Phoenix Homeless Outreach Program, and the company’s flagship Patient-Centered Health Home (Integrated Outpatient Practice). Scott has also worked hand in hand with Police Departments in the East Valley and presents on the subjects of substance abuse and stages of addiction.

Sead Hasic, Business Development/Admission. Sead began his recovery journey in August of 2014. Shortly after, he started his career in the recovery field. Sead became a resident manager at a non-profit organization in the valley that helps hundreds of men and women, daily. Sead then took his experience to Calvary Healing Center where he continued his mission of helping others.

Originally from Toronto, Canada, Celia Cacciotti moved to the Scottsdale area in 1994 with her family to escape the cold weather. Celia has been working in the medical field for the past 8 years.  Celia’s health philosophy is “Balance is key to feeling better and living better – We should honor and tend to our mental, physical and emotional/spiritual well being.” When she isn’t helping clients or being the glue that helps keep Cornerstone together, she enjoys spending time with family and friends, cooking, visiting local farmer’s markets, and traveling.

Max Perez has worked in the behavioral health/recovery field for 4 years and has worked with a community-based outreach team to provide services to clients who suffered from addiction as well as being chronically homeless. Max has a passion for helping those suffering from drug and alcoholic addiction and believes everyone deserves to live a life free from addiction.

Nate McKamie found recovery in April of 2016. After a career in the restaurant business, he found his life’s purpose in helping people find sobriety and has been working in direct client care since Cornerstone’s inception.

Cole Armstrong was born and raised in sunny south Florida only to start his life of recovery here in Scottsdale back in November 2018. Since then, he has traveled this road of helping others find recovery and began working at Cornerstone in January of 2020. As an alumni of the program, he hopes to share and give back the love and understanding of life that Cornerstone once gave him.

Ryan Cain grew up in Akron, Ohio and moved to Scottsdale in December of 2019 to begin his journey in recovery at Cornerstone Healing Center.  He soon after began his career with Cornerstone as a House Manager, claiming, “This program has given me my life back, I’m so excited to be a part of the team and help pass on what was given to me.”.  In his free time he enjoys traveling, hiking, and skydiving. 

Eric Yunker grew up in Chicago and moved to Tempe in December of 2017 to begin his education at ASU.  He soon after began his career with Cornerstone in operations as a House Manager.

Josh Moran grew up in Chicago and moved to Arizona in January of 2020 to begin his recovery journey.  Now he’s a team member at  Cornerstone in operations as a House Manager.

Mikey Candella was born and raised in Phoenix, AZ. Mikey found a solution to drugs and Alcohol in April 2018. He has worked in the recovery field for most of his sobriety. Mikey is a certified yoga instructor and uses that as an outlet, helping individuals to find community, spirituality, and a healthy practice.


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