Bunnell was born in Kansas City, Missouri. He moved to Colorado Springs in 1915 and was thereafter associated with that city. As a WPA artist from 1934 to 1941 he executed many commissioned murals in a sturdy, somewhat abstracted figurative style. He was also noted for his colorful Western landscapes. Later he become particularly known for bold abstracts in a cubist-influenced idiom, tending eventually toward abstract expressionism, the style in which he worked from about the 1950s until his death. Marika Herskovic's American Abstract Expressionism of the 1950s : an Illustrated Survey (New York School Press, 2003), provides an accounting of this period in Bunnell's stylistic evolution. His work is in the collections of the Nelson-Atkins Museum of Art, the Taylor Museum in the Colorado Springs Fine Arts Center, Denver's Kirkland Museum, and others. He died in Colorado, aged 71.