After a three-day siege by Free State forces at Clashmealcon, County Kerry, he died after falling from a cliff onto rocks and then being shot.

He shot a British officer in an ambush led by captain George O'Shea at Shannow Bridge where the Kilflynn road joins the R557, forcing a retreat.

The raiding party received reinforcements; he and his men were eventually surrounded at nearby Clashmealcon on 16 April by Michael Hogan's 1st Western Division.

Three of Lyons' men who'd surrendered, Edmond Greaney, James McEnery and British deserter-turned-republican Reginald Stephen Hathaway, were executed in Ballymullen Barracks by gunshot on 25 April, for breaking their undertaking not to take up arms against the Free State, attacking troops at Clashmealcon, burning the Civic Guard station at Ballyheigue, stripping the same Civic Guards and robbing the post office at Ballyduff.

[3][6][7] [8][9][2][10][11][12][13] He was buried alongside George O'Shea and Timothy Tuomey (both killed at Ballyseedy) in the Republican plot at Kilflynn Church (now St. Columba's Heritage Centre).