There are several articles covering the death of John, his wife Mary, and their son John Jr.
I'll sight one of the articles:
Car swept away in flood -- Plum Creek. Appears to be area of Castle Rock, Colorado. John and family of Lafayette, Colorado. Greeley Daily Tribune, P. 1, via Newspapers.com
Another article from another newspaper stated they were headed to Colorado Springs, to see grandfather (Mr. Hopkins) of John Jr.