It happened around 10:30 p.m. in the 300 block of Governor Printz Boulevard.
Claymont's Alexx White is an army veteran.
Wednesday night just across from his home he heard something like he hasn't since Vietnam.
He said, "My whole house shook. Boom. It was so sudden and it was all over. I said it felt like a Claymore mine."
We have that boom now on video and showed it to him.
You see something being lit than an explosion.
Officials say once police and EMS got to the scene they found a 50-year-old man critically injured in the parking lot.
White says that makes sense.
He said, "I'm standing here on the porch and I looked over and I heard someone around that yellow box across the street. It sounded like someone was moaning."
But it wasn't just White who heard the blast, everyone around here did.
His neighbors John and Mika Cowan heard it.
They said, "It was like a bomb. My kids were scared. My daughter ran upstairs."
Now, this happened just near the end of an automotive shop's parking lot.
They say a motorcycle now parked there isn't theirs.
They believe the man who lit the explosive rode there on the Harley.
For some reason got off and then lit the device injuring himself.
You can see where it happened. White debris is scattered across the pavement.
One of the vehicles parked closest to the blast was damaged in the back.
The state fire marshal's office is leading the investigation.
At this point, they only say an explosive device was used.
They're still determining what kind of device and what the intention of the explosion was.
There is no word yet on who the man injured is.
But he remains in critical condition.