A MAN has tried to down a long-neck at a Territory library and allegedly wrestled a librarian who attempted to confiscate his beer then launched an F-word tirade.

The unknown man pulled out his alcohol at the computer terminals inside Casuarina Library on Friday.

Roper Bar miner Warwick Mylchreest, 22, was waiting to use the printer when he watched the beer battle unfold.

"He pulled out a long neck of Extra Dry and started chugging it," he said.

"He put it down on the desk and the librarian sheila told him it's a library and he can't have it here.

"Old mate jumped up and tried to wrestle her for it. They both had their hands on it.

"Then she said 'you can leave or else hand it over'."

Mr Mylchreest said the man promised to leave if the librarian gave him his beer back. But instead he sat back down at the computer.

Mr Mylchreest started filming the entertainment on his iPhone.

The librarian returned with the manager who told the man she'd call the police.

The man jumped up, shouted "well call the police" and stormed off, shouting the F-word the whole way.

"There were little kids everywhere and the whole place just stopped."

Please enable Javascript to watch this video

Mr Mylchreest, from NSW, said he'd never seen anything like that at a library before.