The Latest: 3rd officer was wounded when bullet grazed neck

The man who killed three Louisiana law enforcement officers purportedly described his actions as a "necessary evil" in a self-described manifesto that an Ohio man says was emailed to him by the gunman less than an hour before the shootings.

The Associated Press obtained a copy of the letter from Yarima Karama, the Ohio man who said he didn't know Long personally, but received several emails from him after Long began commenting on Karama's YouTube videos in March.

Baton Rouge Mayor-President Kip Holden says he will ask the police department to look at changing protocol when officers respond to complaints involving weapons.

Protests rocked the city following the July 5 death of a black man during a confrontation with two white police officers.

The mayor of Baton Rouge has signed up to run for a congressional seat as his city is embroiled in the aftermath of a police shooting, protests and the slaying of three officers who were ambushed by a gunman.

Holden didn't speak much about his congressional campaign plans, saying his focus remains squarely on leading Baton Rouge, where three local law enforcement officers were shot and killed this week and three others were wounded by a black man who targeted police.

The shootings came fewer than two weeks after a black man was shot and killed by white police officers, setting off a string of protests around the city.

Just down the street, on a corner across from the police station, black activist Redell Norman and a handful of supporters who have protested the police shooting of Alton Sterling held a smaller demonstration that included Black Lives Matters signs and forms for anyone who wanted to register to vote.