Lester Davis allegedly fired a gun three times at another customer inside the All Cuts Barber Shop in Wentzville, Missouri, while discussing the Connecticut school shooting.
Davis has been charged with first-degree assault, armed criminal action and unlawful possession of a weapon.
Davis was in the barber shop at about 11:30 a.m. on Tuesday when one of the customers said the Sandy Hook Elementary School massacre "makes me want to murder the suspect," reports the St. Louis Post-Dispatch.
Davis reportedly asked: "You want to murder me?"
He then walked out to his car, got a loaded Smith & Wesson 9 mm pistol, walked back inside the barber shop and fired three shots in the customer's direction.
Davis then said "I'll let you slide," walked out of the barber shop and drove off in his car. Davis is now in jail on a $400,000 bond.
According to court records, Davis was convicted of second-degree homicide and unlawful possession of a weapon in Middlesex County, N.J., in 1975.