A Louisiana police officer providing security at a high school basketball game in New Orleans was shot and killed following a mask-related dispute, authorities said, and a suspect was immediately taken into custody.

Tulane University Police Officer Martinus Mitchum was shot Friday while working at George Washington Carver High School in the 3000 block of Higgins Boulevard, the New Orleans Police Department said.

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John Shallerhorn, 35, was booked early Saturday for armed robbery and first-degree murder of a policeman, Fox 8 reported, citing Orleans Parish Sheriff’s Office jail records.

After arriving at the high school Friday, Shallerhorn allegedly robbed a 39-year-old man sitting in a vehicle in the parking lot, raising his shirt to brandish a firearm and demanding the victim’s medallion chain, police said.

The victim handed the chain to Shallerhorn, who then attempted to enter the school but was stopped for not wearing a mask.

A physical altercation ensued with a school employee, police said, before Mitchum intervened and escorted Shallerhorn out.

Shallerhorn, as he was leaving, allegedly shot the officer twice. He then placed the firearm on the ground and was taken into custody, police said.

Read more at Fox5.