NEWBURYPORT, Mass. (WHDH) — Two people have been charged with assaulting a Salisbury Beach lifeguard, allegedly over the lifeguard's whistle.

The 24-year-old lifeguard was using a whistle to keep swimmers safe, but apparently it annoyed Erin Mulcahy, 24, and Shawn Duncan, 42.

“They were saying that the blowing of the whistle was bothering the person’s hangover. It was apparent when we processed them that alcohol was involved,” said Chief Tom Fowler of the Salisbury Police Department.

The lifeguard explained that blowing his whistle to warn swimmers was part of his job.

“They threw some water at the lifeguard and then physically assaulted him,” said Fowler.

“It’s awful. I’ve been coming to this beach for 30 years and I’ve never heard of anything like that in my life,” said David Wagner, a beachgoer.

Police said Duncan threw a punch and Mulcahy pushed the lifeguard down and also hit him.

Police said Mulcahy threatened the responding officer. When the lifeguard arrived at the police station to give his statement, Duncan yelled threats at him, saying he knew the identity of the victim and would harm him.

“Basically that we wouldn’t stand for that and this is a victim and someone giving us a statement, so [Duncan] was appropriately charged,” said Fowler.

Mulcahy and Duncan have been banned from the beach and are not allowed near the lifeguard.

The pair pleaded not guilty Monday in Newburyport District Court to charges including assault and battery on a public employee, resisting arrest, threatening a witness and disorderly conduct. They will return to court on Aug. 26.

The Associated Press contributed to this report.

Join our Newsletter for the latest news right to your inbox