LENNOX, S.D. (AP) — Sioux Steel workers in Lennox are marking the one-year anniversary of a workplace shooting that left two dead and two others seriously injured.

Scheduled memorial events Friday included a private dedication of a memorial plaque, a balloon release and a private memorial service.

Authorities say Sioux Falls truck driver Jeffrey DeZeeuw got into an argument Feb. 12, 2015, with a supervisor at a Sioux Steel location called ProTec and fatally shot Richter and wounded a woman before killing himself. Authorities say DeZeeuw also injured another male worker who confronted him.

CEO Scott Rysdon says the incident was a "senseless loss" of friends and family.

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