A shirtless New Zealander who saw the Capitol Hill shooting unfold has found instant fame as the "Bro Witness".

Matthew Jacobs, 26, followed the shooting drama on his rented bike after seeing a black sports car trying to ram through a temporary barricade at the White House.

He was mobbed by reporters, many of whom tweeted about his no-shirt and Miami dolphins cap ensemble.

National Journal journalist Matt Vasilogambros quickly dubbed him "Bro Witness".

Bro witness pic.twitter.com/Wf3Xg3HH6q

That post was retweeted hundreds of times.

Several major US media outlets have now done stories on Jacobs, with Buzzfeed compiling all the known facts about him.

The New York Magazine says "Bro Witness" is now "New Zealand's No 1 celebrity".

Vanity Fair headlined its coverage of Jacobs 'Shirtless Brostander Effortless Diverts Debate Away From Gun Control and Government-Shutdown Safety' while Michael Roston of the New York Times said Jacobs was a "witness to brostory".

Star media witness from NZ Matthew Jacobs witnessed incident; starte d pic.twitter.com/G9Ls9FpSih

Jacobs told reporters he had "followed the car with the chick in it" from the White House, Daily Beast reporter Ben Jacobs said.

Friends of the "Bro Witness" labelled him a "f***head", Jacobs said.

Jacobs already has his own entry in Bro Bible, the online repository of all things 'Bro'.

- nzherald.co.nz