The officers failed to notify higher-level commanders when they became aware of "escalating issues" involving Robert Card, and did not conduct a required investigation after he was hospitalized for mental health problems months before the shooting, the military said.

The 40-year-old sergeant first class shot and killed 18 people at a bar and a bowling alley in October 2023, sparking a two-day manhunt before he was found dead of a self-inflicted gunshot wound.

Lieutenant General Jody Daniels, the head of the US Army Reserve Command, ordered an investigation into his death and conduct in the months leading up to the shooting.

"The investigation recommended adverse administrative action be taken against three officers in SFC Card's chain of command for dereliction of duty. The adverse actions have been completed," an overview of the probe said.

It said this punishment means in effect they cannot be promoted any further and will stay at their current rank, which were colonel and below.

In remarks to journalists, Daniels detailed what he said were mistakes by Card's chain of command in the months before the shooting.

"As Sergeant Card's leadership became aware of escalating issues through contact with fellow soldiers and family members, they failed to submit a Commander's Critical Information Requirements report to higher-level commanders or contact the army insider threat hub," Daniels said.

Card was hospitalized in a civilian mental health treatment facility and was released in August 2023, but his unit did not conduct a required investigation to document his condition and hospital stay, which would have allowed the government to pay for treatment, she said.

Daniels also noted that when Card was released in August 2023, "his chain of command was not provided with any information regarding his diagnosis, prognosis or discharge instructions."

The shooting -- which took the lives of victims ranging from a 14-year-old to a couple in their 70s -- was one of the deadliest in the United States since 2017, when a gunman opened fire on a crowded music festival in Las Vegas, killing 60 people.