Meet Williams & Schiller, PC

Who we are

At Williams & Schiller, PC, we are focused on building relationships that endure with personalized, attentive service. With offices in Sandpoint, Idaho and Fargo, North Dakota, we work with individuals and small businesses based in both our hometowns – and around the world. Whether you’re local or afar, get in touch!

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Our CPA Professionals

Our staff of knowledgeable professionals can assist with your tax, accounting and financial planning over the long term. Our goals are to provide our clients with long-term financial and tax planning advice. We also provide our clients with up-to-date guidance regarding U.S. reporting and tax changes. 

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Sandpoint office • Managing Partner


Born and raised in Libby, Montana, Brad went on to earn his BS in Geology, and further focused on graduate work in accounting and finance at the University of Montana. He achieved the CPA designation in 1987, and began his career with the ‘Big Four’ accounting firms – KPMG in Billings, and Coopers and Lybrand in Spokane, Washington.
Brad honed his expertise to provide tax planning, preparation and accounting services to businesses and their owners, as well as to individuals. He relocated to Sandpoint, Idaho in 1991 and opened his own firm. In 1995, he merged his private practice with fellow local CPA Paula (Freeman Parsons) Hall, creating Williams & Parsons, PA, CPAs. In addition to being a CPA, Brad holds the designation of Personal Financial Planning Specialist. Brad is also an accredited Peer Reviewer, providing reviews to other CPA firms around the western US to help them maintain their firms’ system of quality control.

Skype: brad.j.williams
Let us do the work, call or email today!

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Fargo office • Managing Partner


Mark began his career in 2001 working for CPA and investment advisory firms in Minnesota. Mark was a
partner in our Sandpoint office before moving back to Minnesota in 2012, and subsequently to open our
Fargo office in 2019. Mark specializes in comprehensive wealth management including portfolio
construction, investment management, estate planning, insurance needs analysis, tax planning,
business consulting, and business valuations. In addition to being a CERTIFIED FINANCIAL PLANNER
(CFP®) professional, Mark is also a CPA and is Accredited in Business Valuation (ABV).

Mark received his B.A. in Accounting from Concordia College, Moorhead, MN. He also holds graduate
certificates in Estate Planning and Financial Analysis from the College for Financial Planning.
Mark enjoys all things outdoors and resides in Moorhead with his wife Kristi, and their two children.

Let us do the work, call or email today!

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Certified Public Accountant


Brett Sweezy was born and raised in the North East, hailing from New Hampshire and Vermont. He graduated the top of his class from New England College, earning a Bachelor Degree in Accounting with a Minor in Economics. Brett is a CPA and from 1992-1999, he owned and managed his own Sandpoint-based accounting firm (Brett Sweezy, CPA, PA), providing accounting and tax services to more than 300 clients.

Following the sale of his successful business, Brett transitioned his career to corporate finance. He has an extensive resume of serving as the CFO and/or President of several national and international companies, and can claim 25+ years of experience in all financial aspects of both public and private companies, as well as issues important for individuals.

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Mariah Williams, MBA, CPA, CMA

Mariah was raised in Sandpoint, Idaho, and received her Bachelor’s in Accounting and Master’s in Business Administration from the University of Montana.  In addition to being a Certified Public Accountant, Mariah is a Certified Management Accountant – the leading global certification for strategic financial management in business. Mariah brings expertise in accounting and financial reporting, high-net-worth individuals and families, and private foundation and non-profit accounting and tax-related concerns.

Mariah joined the Sandpoint office of Williams & Schiller in 2020 and is thrilled to be back home with her husband Tucker enjoying all the outdoor activities North Idaho has to offer.

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Mikayla Cargile, CPA

Mikayla was born and raised just outside of Fargo, North Dakota. She graduated from Hope High School and received her bachelor’s degree in Accounting at Minnesota State University Moorhead in December of 2019. She received her CPA designation in 2022.

Mikayla joined the Williams & Schiller team at the Fargo office in the summer of 2019 and has worked closely with partners and managers ever since to specialize in tax preparation and consultation for individuals and for small businesses.

She spends most of her weekends with her husband and her dog. In the summer, she often travels to the lake and enjoys the outdoors. In the winter, she likes to stay in and work on home projects. She also has a knack for traveling and seeing the world, including a visit to Africa with her husband in 2021.

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Senior Associate

Cheryl O’Boyle, CPA

Cheryl was born and raised in the Spokane area, and spent most weekends in her Grandpa’s hand-built cabin on Garfield Bay. She graduated from Cheney High School and received her BA in Business Accounting from Eastern Washington University. Cheryl achieved her CPA in Washington State in 2016, and joined the team at Williams & Parsons in 2018.

Now residing in Grandpa’s cabin on Garfield Bay with her husband and two children, she enjoys boating, skiing, long walks around the lake, reading and crafting. Cheryl also served as Treasurer for Job’s Daughters #44 in Spokane, and has been a member of the Order of Eastern Star – Victory Chapter for more than 3 years.

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JACKIE WINDJU, Bookkeeping, Payroll, Quickbooks Pro Advisor

Jackie Windju is the third generation of her family to make this lake-and-mountain town home. After graduating from Sandpoint High (go Bulldogs!), she earned her BA in French and Business from the University of Idaho, and continued on to get her Masters in International Management from the American Graduate School of International Management.

Jackie started her career as an accounting supervisor with Sullivan Payne in Seattle, Washington, then moved on to become a Risk Manager for the Seattle Times. She returned to Sandpoint in the early 1990s to start her family and to grow in her chosen field.

Jackie has worked for a local CPA firm since 1992, and has been with Williams & Parsons since 1998. She is a full service bookkeeper, payroll specialist and a QuickBooks Pro Advisor. She has taught QuickBooks classes through North Idaho College’s Workforce Development Center, and is always available to answer QuickBooks questions for her clients.

When she is not working, she spends time with her family and friends and enjoys hiking, skiing, riding her cruiser-style bike, and traveling the world.

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MAGGIE HAYES, Senior Associate

Maggie Hayes is a Senior Associate in Accounting Services in our Fargo, ND office. She has more than 15 years’ experience, with a vast tax and accounting background among various industries.

Maggie graduated from the University of Minnesota, Duluth, with a bachelor’s degree in accounting. From there, she spent several years with a mid-size CPA firm in the Twin Cities area, focusing on small-to-medium sized business tax. She and her family then moved to the Fargo area to be closer to extended family, where she worked at a large CPA firm in the Business Outsourcing group before joining Williams and Schiller, PC in early 2021.

For fun Maggie enjoys time at the lakes with family, and watching her two sons play baseball.

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