UTC freshman Vanessa Parks didn't know what to expect late Thursday night when she decided to attend the rave at the Lupton Library, an event she had heard about from messages online.

When she approached the library, she said she saw hundreds of students gathered and dancing, music blaring in the background and some guys jumping off the building. Then suddenly the atmosphere became panicked.

"All the sudden I saw girls running backwards," said Ms. Parks. "As I turned, a cop sprayed Mace in my face. The cop chased after me. I was scared because I hadn't done anything wrong, and my face was burning. I didn't know what to do."

Ms. Parks is one of dozens students who were Maced Thursday night and are outraged about what they see as police brutality.

"There was no property damage; there was no vandalism. No one was getting hurt," said Ms. Parks, who said her friends had to help her wash the Mace off her body.

Officials say police acted appropriately to a dangerous and disruptive scene. A group of nearly 1,000 attempted to storm the library doors and chanted "Let us in! ... Take the library," a University of Tennessee at Chattanooga news release stated.

Some students threw items at the police officers, said Chuck Cantrell, a spokesman for the university.

The library was closed for a little more than an hour to allow the crowd to disperse and police regained control of the site, he said.

UTC student Nicholas Chad Rush, 18, was arrested at the gathering and charged with assault after police said he threw a water bottle that struck an officer in the face. Three other students, Aaron Schoolfield, Patrick Wright and Marques Donald also were arrested and charged with disorderly conduct, said Sgt. Rick Mincy, spokesman for the Chattanooga Police Department.

"I know that some of the students believe this was a harmless gathering, but when you try to force your way into a building and jump off buildings, then you've gone beyond harmless fun," said Mr. Cantrell. "We are the middle of exam week, and there were students inside the library trying to study and conduct research, and this crowd disrupted the operation of the library."

UTC Chancellor Roger Brown said UTC police officers acted appropriately and said campus leaders will work to prevent future events from reaching a flash point.

Chattanooga Police Chief Freeman Cooper was out of town and unavailable for comment.

According to police reports, students had gathered at the library for a party at 11 p.m. that had been publicized via text message and online social networks such as Facebook, Twitter and blogs.

Mr. Cantrell estimated that the crowd numbered more than 1,000 students. However, some students and police say it was closer to 200 or 300.

UTC senior Jenny Adkins said the party was intended to be modeled after a 2008 rave at the University of North Carolina which occurred inside the school's library. Students at UNC used the Internet to tell students about the event, she said.

Text messages about the UTC party began circulating among students last Sunday, said UTC sophomore Mario Howard, who was present at the library Thursday night.

He said the librarians knew about the rave and Dean of Libraries Theresa Liedtka reportedly told library employees to allow it to go on. Mr. Cantrell said librarians knew there were rumors that the rave would take place, but did not approve the event.

Ms. Adkins said students were stage-diving off a portion of the building when police arrived with Mace.

"They were Macing the students," she said. "They were pulling it out and waving it around like Febreze."

When the crowd began to disperse, some students were trampled, she said.

"Students were being stupid ... but I just don't think the cops acted correctly," she said.

UT student Ryan Miller, 19, said he was Maced and had to run and cover his face.

"(I feel) oppressed, as in they're abusing their authority," he said. "They came out and used physical force and I don't think it was needed. My parents and my lawyer will hear about this."

Other students were taken down to the ground with force, some students said.

Nakima Eddins, a freshman at UTC, said she saw a student who was jumped on by police after being Maced.

"The student apparently swung at the police, and they then threw him to the ground," she said.

Carlazjion Constant, also a freshman, said he saw one man being attacked by a swarm of police officers.

"And then there were 15 of them on this one dude and then they threw him on the ground and they were hitting him," he said.

Mr. Cantrell said he believes the student gathering was intended to be harmless fun, but as the crowd grew larger and larger and began trying to get into the library, police were unsure of the students' intent.

"They took the position that they needed to protect the library," he said. "When they told the crowd to disperse, some of the students didn't. Things just escalated from there."

In the future, Dr. Brown said officials will be on guard for raves or parties being advertised on Facebook or other social networking sites. If campus leaders know about a planned event, officials can talk with students about their intentions and work to ensure their safety.

"We are going to try to do an earlier and quicker response when we start to see text messaging or social network messaging," he said. "I am not certain we can change one of these events on the spur of the moment, but we would certainly like the opportunity to try."