PORTLAND (AP) – The University of Southern Maine on Friday canceled an art exhibit showcasing the paintings of a prison inmate who killed a New Jersey state trooper 25 years ago and had cast himself as a political prisoner.

The exhibit had drawn outrage from police agencies that said it painted an unfair picture of artist Thomas Manning, who is serving 80 years in prison for the 1981 killing of Trooper Philip Lamonaco after a traffic stop.

USM President Richard Pattenaude said the exhibit was designed to spark discussion about political dissent in society, but had become overshadowed by Manning’s background and criminal history. The exhibit, he said, had become “misunderstood and needlessly divisive.”

“What was to be a forum has become a battleground,” Pattenaude said.

The exhibit, which opened on Sept. 1, was taken down Friday afternoon. A symposium to discuss political prisoners and political dissent will go on as planned in October.

Manning, a former Portland resident, was part of a group of political radicals that robbed banks and bombed buildings in the 1970s and early 1980s to protest what some government critics called racism and U.S. imperialism. Organizers said the exhibit – titled “Can’t Jail the Spirit: Art by Political Prisoner Tom Manning and Others” – was intended to spark debate.

But the event drew criticism from law enforcement groups.

George Loder, vice president of the Maine State Troopers Association, said police felt that the exhibit glossed over Manning’s violent history. Loder said he was happy with the university’s decision.

“Don’t say he’s a political activist when in fact he’s a terrorist,” Loder said.

At Pattenaude’s press conference announcing the end of the exhibit, several students and exhibit organizers said they felt that the university was censoring free speech.

Jonah Fertig, an organizer with the Victory Gardens Project, a group that supports what it views as political prisoners, held up a sign reading, “USM Suppressing Free Speech.” He said the university is allowing itself to be controlled.

“It seems to me that we are entering into a police state and censorship of free speech,” Fertig said.