The pilot of a small twin-engine airplane died Monday after crashing into a delivery truck and a building near the San Luis Obispo County Regional Airport shortly after takeoff.

All the employees working in the Promega Biosciences building on Granada Drive escaped injury in the crash, which occurred at about 1 p.m.

Serafin Armenta, the driver of a FedEx truck that the plane crashed into, had walked away from the truck only moments before the crash, and also was unhurt.

“I heard a loud boom, looked back and saw part of the tree fall, and then something caught on fire,” Armenta said as he stood at the scene with ashes still in his hair.

The pilot, who has not yet been identified by authorities, was the only person on board the plane, which was recently purchased in Napa, and is registered to a business in downtown San Luis Obispo.

The charred FedEx truck was all that stood between the plane and the back end of the Promega building used for shipping and receiving — likely preventing the shattered remains of the aircraft from further impacting the building.

First responders, concerned about the potential for chemical contamination because of hazardous chemicals stored at Promega Biosciences, evacuated the surrounding business park until it was clear that the plane had not breached the building.

“This could have been a major hazmat incident, but we dodged it all,” said San Luis Obispo Fire Chief Charlie Hines. “It is unfortunate for the pilot, but it could have been a lot worse.”

The plane’s pilot made a mayday call around 1 p.m. to the airport.

Fire engines were en route to the scene, about 1.5 miles northwest of the airport, before it crashed.

The plane, which departed from the airport only moments before, clipped a set of power lines and scraped the cinderblock back end of the Promega building before crashing into a tree and the FedEx truck parked behind the building.

A witness at the scene told investigators that he saw the pilot struggling with the plane’s controls right before it crashed.

Angel Sosa, who works nearby at Del Ozone on Granada, said employees there heard an explosion and went outside to see that the small plane hit the FedEx truck.

“I saw pieces of it everywhere,” said Sosa, who ran to the scene with a fire extinguisher to try to help put the fire out.

Afterwards, Promega Biosciences employees waited for updates down the block from their office, checking cell phones and talking.

One employee, who had gone down the street for lunch without his cell phone, was the last of the 55 employees to be accounted for.

The employee came running back to the scene once he heard what had happened, and was greeted by fellow employees with hugs and words of relief.

Kris Yetter, president of Promega Biosciences, said she was glad all of the employees had made it out unharmed.

“I feel very fortunate that it wasn’t any worse than it was,” Yetter said. “I feel so sorry for the family of the pilot.”

The pilot was flying a Cessna 337 Skymaster, which has one engine in front and another in the rear of the aircraft.

The Federal Aviation Administration and the National Transportation Safety Board are investigating the accident.

Click here to read updates on the story from the San Luis Obispo Tribune.

Tribune staff writers Cynthia Lambert and Julie Lynem contributed to this story.

AnnMarie Cornejo is a reporter with the San Luis Obispo Tribune. Contact her at acornejo@thetribunenews.com, or 805.781.7939. Stay updated by following @a_cornejo on Twitter.