GRETNA - The man who fatally shot former NFL player Joe McKnight has pleaded not guilty to a second-degree murder charge.

A lawyer for 55-year-old Ronald Gasser told reporters after Monday's arraignment in the New Orleans suburb of Gretna that McKnight's death was a case of justifiable homicide.

Gasser, from Terrytown, had initially been arrested on a manslaughter charge. Last week he was indicted on a second-degree murder charge, which carries a mandatory life sentence. He's jailed on a $750,000 bond.

McKnight, who played for the New York Jets and the Kansas City Chiefs, was killed Dec. 1. Authorities have said the 28-year-old McKnight, who was black, and Gasser, who is white, were driving erratically and yelling at each other on a New Orleans bridge prior to the shooting.