American architect Bill Hellmuth, who designed many projects as president and then CEO of global architecture studio HOK, has passed away aged 69 after a long illness.

The architect died on 6 April following a long illness, according to a statement published on the HOK website, which remembered Hellmuth's life and work.

The firm described him as "an extraordinary architect and leader".

Born in 1953, the architect served as president of HOK and design principal for the studio's Washington DC office from 2005. He was also named CEO in 2016 and chairman a year later.

Hellmuth was known for his "hands-on" approach to designing buildings, overseeing dozens of projects across 20 countries during his career at HOK – from offices and embassies to museums and hospitals.

These include the UAE's 75-storey Abu Dhabi National Oil Company Headquarters and the King Abdullah Petroleum Studies and Research Center in Riyadh, Saudi Arabia.

Hellmuth designed many buildings in the US such as The Steven F Udvar-Hazy Center in Virginia – an extension to the Smithsonian Institution's original HOK-designed National Air and Space Museum.

Late HOK co-founder Gyo Obata, who passed away last year aged 99, served as a long-standing mentor to Hellmuth after encouraging him to join HOK in 1991.

Under Hellmuth's hand, HOK produced hundreds of green-certified projects and over 400 designers achieved "green" certification, according to the architecture studio.

The architect also launched the HOK Diversity x Design Scholarship in 2021, which awards annual scholarships to underrepresented design students.

"Hellmuth was exceptionally optimistic about the ability of design to improve people's lives," said the studio.

The architect attended the University of Virginia in the 1970s, earning a Bachelor of Science degree in Architecture.

He then went on to receive a Master of Architecture from Princeton University where he studied under the late architect Michael Graves. After graduating, he joined Chicago-based studio Skidmore, Owings & Merrill.

Over his lifetime, Hellmuth won 29 awards for his work from the American Institute of Architects (AIA).

The AIA elevated him to its College of Fellows in 2017, while the University of Virginia's School of Architecture presented Hellmuth with its Distinguished Alumni Award the following year.

The architect was the nephew of HOK co-founder George F Hellmuth who helped to establish HOK under its former name Hellmuth, Obata + Kassabaum in 1954.

Bill Hellmuth is survived by his wife, Nancy, as well as his daughter Grayson and her husband, Cleve Rueckert, and his son William and his two grandchildren.

The images are courtesy of HOK.