PITTSBURGH  The man charged with killing three police officers here on Saturday was a contributor to racist Web sites, writing about his hatred of race-mixing, the economic collapse, Zionist conspiracies and his fondness for his “AK” rifle.

The police said the three officers were killed, and a fourth wounded, after they responded to a domestic disturbance call early Saturday at the home of Richard A. Poplawski, 22. The police said Mr. Poplawski shot the officers with his AK-47 rifle.

He sometimes wrote about what he saw as a Zionist conspiracy, as in a March 13 post: “One can read the list of significant persons in government and in major corporations and see who is pulling the strings. One can observe the policies and final products and should walk away with little doubt there is Zionist occupation and  after some further research & critical thinking  will discover their insidious intentions.”

After the Pittsburgh Steelers won the Super Bowl, Mr. Poplawski dismissed football as nothing but “negroball.” Then, instead of celebrating the victory, he went out and did reconnaissance on how the police tried to control the crowds and posted his findings.