BRIDGEWATER -- No one knows who he is or why on a recent July afternoon he decided to venture out on the front lawn of a home, shirtless, to thrash hardcore metal riffs on his electric guitar.

There is only one clue: a green spray painted sign that simply read, "FREE METAL."

But millions of people have now seen and listened to the fast, intense guitar tones by the unknown guitarist -- who was also sporting a straw hat and a red cape -- after a passerby filmed him with his cellphone earlier this month.

Currently, the video has been viewed more than 6.6 million times, according to a report by the Daily Mail.

Steve Brown, a 38-year-old Bridgewater native, took the footage after spotting the shirtless musician while driving through the quiet, seemingly undisturbed suburb.

He didn't know the man, and it remains unknown whether the guitarist was playing in front of his own home.

Brown was with his girlfriend, Antoinette Karis, 38, who can be seen enjoying the free concert while sitting in the passenger seat of the car. Their dog, Oliver, was sitting in the back, also gazing at the spectacle.

For some, the free metal concert might have appeared out of place. But for Brown, he saw a perfect depiction of the rich underground metal and hardcore music scene that for decades has been entrenched in Bridgewater.

Several prominent underground bands have come out of the township.

"There has always been an underground punk scene there," said Brown, 38, who now lives in Raritan Township with his girlfriend. "It has a pretty rich history."

In the footage, the guitarist does not appear at all affected or self-conscious by the strangers recording him. In fact, the guitarist gave the couple an affirming nod before continuing.

"He wasn't playing for us," Brown said. "He was playing when we pulled up and continued playing when we drove off."

Brown added, "He just seemed confident -- that he decided to take his gear (and) put a sign up. That is what I really dug; playing as if 'I don't care, you dig it or you don't and keep driving.'

Spencer Kent may be reached at skent@njadvancemedia.com. Follow him on Twitter @SpencerMKent. Find the Find NJ.com on Facebook.