The ambush rocked a city still shaken from days of angry protests and tension over the fatal police shooting on July 5 of a 37-year-old black man, Alton Sterling, who was confronted by officers while selling CDs outside a Baton Rouge convenience store. Sterling was buried just last Friday.
A day after his slaying, another black man, Philando Castile, 32, was shot to death by a policeman during a traffic stop near St. Paul, Minnesota.
The back-to-back killings reignited nationwide protests over the use of force by police against minorities, including a fateful rally in Dallas on July 7 that ended up shattered with the deadly ambush of five police officers by a gunman apparently out to avenge the deaths of Sterling and Castile.
Police declined on Monday to say whether the attack by Long, who was black, was racially motivated. Two of the lawmen killed on Sunday were white, and a third, Montrell Jackson, 32, himself was black.