As the mayor explained the importance of not mixing households during the pandemic, he was interrupted by the sound of a man shouting "f*** you in the distance.
A sign language interpreter, who stood two metres apart from Mr Caldwell, did not skip a beat as she broke from translating the mayor's responses to hold up her middle finger to the sky to show what the heckler had yelled.
"Someone with strong opinions about what we're doing," said Mr Caldwell as he pointed behind him in reference to the heckler.
He added that he had been recently experienced a lot of heckling when protesters against the lockdown came by his house.
"We allow that in our country," said Mr Caldwell. "Free speech is critical, and I understand how upset people are."
During the briefing, the mayor also announced that parks, beaches, and hiking trails would reopen for solo activities that include meditation, reading and jogging.
However, gatherings remain strictly banned.
Hawaii has recorded a total of 10,025 infections and 88 deaths since the Covid-19 outbreak.