A Wisconsin teacher who posted an anonymous comment online sarcastically praising the Columbine High School gunmen won't face criminal charges, a prosecutor said Wednesday.

Washington County District Attorney Todd Martens said the comment left by James Buss was offensive and disgusting, but was protected speech under the state and U.S. constitutions.

Buss, 46, a high school chemistry teacher in suburban Milwaukee, was arrested by police last week for a Nov. 16 post on a conservative blog that covers Wisconsin politics.

During a discussion over teacher salaries, Buss wrote that Columbine killers Eric Harris and Dylan Klebold "knew how to deal with the overpaid teacher union thugs. One shot at a time!" He added that the gunmen, who killed 12 students and one teacher in the April 1999 attack, should be remembered as heroes.

Martens said Buss was being facetious because he was tired of reading negative comments about teachers.

Martens said he could not charge Buss with a crime because the blog was not likely to incite "imminent lawless action." He said it was unclear whether the comment advocated violence against teachers, and even if it did, its language was not likely to incite others to act.

Buss is a former president of the teacher's union in Oak Creek, where he has worked since 1994. He has been placed on paid leave while the district investigates the incident and considers disciplinary action against him.

Police had asked the district attorney to charge Buss with disorderly conduct and unlawful use of computerized communications systems. But bloggers and free speech advocates had called on him to drop the case.

Martens disclosed his decision not to charge Buss on Wednesday in a letter to Patricia Herdrich, superintendent of West Bend Joint School District No. 1, where a teacher complained about the post.

Dorreen Dembski, a spokeswoman for the West Bend district, said it respects the decision not to charge Buss. "It is very important to us that all threats are taken seriously," she said. "This was turned over to the authorities. They did their work and we'll respect that."