Duke Webb, 37, faces three counts of murder and three counts of first-degree attempted murder for injuring three others in the shooting at Don Carter Lanes, in Rockford, on Saturday evening.
According to Army service information, Webb had four deployments to Afghanistan, the most recent once ending in July.
His lawyer, Elizabeth Bucko, also told the hearing in a Winnebago County courtroom that Webb appeared to have issues with memory loss.
Webb was taken into custody shortly after the shooting and without officers firing a shot, Rockford Police Chief Dan OāShea said Sunday.
At a news conference Monday afternoon, Winnebago County Stateās Attorney J. Hanley said that Webb was in the Rockford area visiting family.