What was the name of William Tell's son who had the apple shot off the top of his head?

"William Tell and his young son Walter..."

[ mises.org/fullstory.aspx?control=1478 no longer exists ]
https://mises.org/library/william-tell-tax-rebel

There is just one small problem: many historians doubt that Tell ever shot an apple off his son's head in 1307 or sparked the Swiss struggle for independence. In fact, many doubt that William Tell ever existed. Instead, Tell's oft-told tale is a product of mangled chronologies, borrowed folk tales, and ample helpings of wishful thinking. But that hasn't kept him from becoming a beloved symbol of Switzerland's national character.

[ smithsonianmag.si.edu/smithsonian/issues04/aug04/tell.html no longer exists ]
http://www.smithsonianmag.com/ist/?next=/history/in-search-of-william-tell-2198511/