Test pilot Charles Schwartz, 50, was killed in the Tuesday afternoon crash near from Fitchburg Municipal Airport, according to state police.
It was the fifth fatal plane crash in Leominster since 1999 and the third this year, according to Mayor Dean J. Mazzarella.
The experimental, single-engine plane slammed into the R&S Machine Shop on Monarch Street, several hundred feet from the airport, around 3:45 p.m., tearing off part of the shop's storefront and roof.
Monarch Street resident Roland Rivard, 39, said the fire was extinguished by about 4:20 p.m.
``I was only about 10 or 15 feet away'' from where the plane crashed, said Nathan Sanborn, 64 the shop's owner and the only person inside the building at the time. ``That is why my knees are still shaking.''
The shop's five employees usually quit for the day around 3:30 p.m.
A spokesman for the Federal Aviation Administration said the homemade aircraft was registered to Andrew San Clemente, of Shrewsbury.
Clemente's mother told The Boston Globe that Schwartz was a test pilot.
According to FAA records, San Clemente obtained a private pilot license for a single-engine plane on Aug. 14, and a temporary certificate for the aircraft that took effect a week ago and expires Nov. 19.
The crash remained under investigation.
