Two men have been arrested after a man was thrown through the window of Hastings Library on Thursday.
The pair then allegedly climbed out the window and continued to assault the thrown man.
The attack, in front of shocked library onlookers, took place just after 11am.
Witnesses told Hawke's Bay Today a group of five men and one woman with a child were involved in an argument inside the library for about 10 minutes before it escalated.
One of the group was wearing a Mongrel Mob patch and witnesses said the argument appeared to be gang-related.
A police spokesperson said they were called to a report of disorder at the library at 11.05am, during which one person was understood to have been assaulted.
However, by the time police arrived, those believed to have been part of the assault had left the scene, the spokesperson said.
Follow up inquiries on Thursday led to two arrests, the spokesperson said.
The condition of the man thrown through the window was unknown and a St John ambulance spokeswoman said they were not called to the scene.
Drops of blood could be seen on the carpet of the library beside the window on Thursday morning.
The library was reopened after a 20-minute closure and the window was hastily repaired.
Hastings Mayor Sandra Hazlehurst said any violent behaviour in the community would not be tolerated.
"Our facilities will remain safe for all of our people and that is why City Assist and Kaitiaki were established.
"We will be reviewing what happened because keeping our community safe is our first priority."
Hazlehurst said Kaitiaki staff members (Library Guardians) had acted promptly and appropriately to contain the situation and keep patrons and other staff safe until police arrived.
It's the second time police have been called to the library this week. Thursday's incident follows a report of a verbal disagreement at the library on Saturday about 1pm.
A police spokeswoman said there was nothing to suggest that particular incident included fighting, or was any relation to gangs.