An ex- US Marine killed three police officers in Baton Rouge, Louisiana in an incident similar the July 5 Dallas attacks, where another former black soldier killed five cops.
The man identified as Gavin Long of Kansas city went on a shooting rampage on his 29th birthday that left two police officers and a sheriff's deputy dead, reports said.
Police officers who responded to shootings killed Long in a gunbattle after the other officers were ambushed.
They have not officially released the names of the victims but one was identified as Officer Montrell Jackson. Law officers Matthew Gerald and Brad Garafola were also killed. That was corroborated with social media posts.
The gunman also critically injured a deputy who is "fighting for his life", said East Baton Rouge Parish Sheriff Sid Gautreaux.
Another wounded deputy and police officer have non-life-threatening wounds, law officers said.
We as a nation have to be loud and clear that nothing justifies violence against law enforcement," President Obama said, while condemning the attack.
"Attacks on police are an attack on all of us and the rule of law that makes society possible," CNN quoted the President as saying.