The incident took place at the Vermont Gurdwara in Los Angeles, also known as the Hollywood Sikh Temple.
A witness confronted the vandal and caught him on cell phone footage walking away from the gurdwara's wall without any explanation, NBC Los Angeles reported.
"I said I was going to call the police on him at which point he said he felt threatened," Karna Ray, the witness who filmed the vandalism, said. "He said, 'I will slit your throat'".
Hollywood police were investigating the hate messages written on the side of the gurdwara.
Ray, who is from New York, was visiting a friend on Thursday when he saw the man writing long incoherent messages with a black maker on the pristine white wall of the gurdwara and started recording him with his cell phone.
He then uploaded the video on Facebook and received thousands of comments.
Ray was particularly disturbed by one of three separate passages calling for the "nuking" of Sikhs, according to Fox 11.
According to a Facebook post by Ray, the vandal flashed a razor at him as he made his threat.
Ray said the hateful message left on the walls of the gurdwara counters everything the Sikh community stands for.
A member of the gurdwara hoped to invite the vandal to a service so he could experience what the community believes in.
"I would love to invite the person in the temple, make him, show him what he is missing," Sarab Gil was quoted as saying.
Nirinjan Singh Khalsa of California's Sikh Council is in close contact with the Los Angeles Police Department about the case.
"This particular incident isn't a matter of swastikas and 'go home, ragheads,' which we get sometimes," Khalsa said.
"This seems to be a diatribe by someone who may or may not be mentally imbalanced," he said.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)