New Hampshire authorities promised to investigate and prosecute rioters responsible for the “disturbing’’ events during the Keene Pumpkin Festival, officials said in a press conference on Monday afternoon.

Keene Police Chief Kenneth Meola said the “riotous behavior’’ began around 1 p.m. on Saturday when two large gatherings of about a thousand people each started throwing rocks and bottles. Police resorted to using riot shields and pepper spray to keep the crowd at bay.

More than 30 people suffered injuries, all of them blunt force trauma from thrown items, Meola said. Eighty-four people were arrested at the festival over the weekend, he said.


“The damage was disturbing,’’ New Hampshire State Police Col. Robert Quinn said, citing the full liquor bottles and billiard balls allegedly thrown at police officers in particular. “To turn your aggression toward another human being in the manner that they did is what I characterize as extremely serious.’’

In addition, Quinn lauded the “tremendous effort’’ of police in dispersing crowds without any serious injuries.

Four unidentified people stood atop an overturned vehicle during mayhem after Keene, N.H.’s annual Pumpkin Festival. —Jeremy Fox/Boston Globe Staff

Meola said police will review video and images from the event in an attempt to prosecute the “heavy hitters’’ of the mayhem, including the students who vandalized and overturned a vehicle. Quinn said there was the potential for first-degree assault charges for those who threw projectiles at police.

Last weekend’s Pumpkin Festival may be the city’s last. Keene Mayor Kendall Lane said city leaders will assess the future of the event in December.

“This was a horrible event that took place,’’ Lane said.

Keene State College president Anne Huot said she was “gravely concerned’’ by the destruction. She reiterated her point on Sunday that students who participated in the riots could face suspension or expulsion from the school.