A New York man who blew off his arm lighting fireworks at an Independence Day party was told the severed limb could not be reattached, the New York Post reported Monday.

Relatives of the 36-year-old victim broke the news to him Sunday, one day after the mortar blew off his left arm outside his Long Island, N.Y., home, as he leaned over to light the explosives and failed to get out of the way in time.

"What's the extent of the damage?" a still-dazed Eric Smith scribbled with his right hand to his family from his hospital bed.

"He didn't realize how far it [the limb] was gone," said Smith's uncle, Paul Gilbert. "He lost his whole arm. "He's going to have a rough road ... a couple of tough weeks ahead of him. They could not attach the arm. It's severed from the shoulder down."

Smith's wife, Tania, saw the horrifying accident from her kitchen window.

"I ran out to see if he was alive," she said.

She said her husband "is more worried about us than himself ... I could use some prayers."

The couple has two kids.

Friends and relatives who were attending a barbecue in Smith's back yard rushed around to the front after hearing the boom when the explosive fired into his shoulder shortly before 6pm local time Saturday.

Smith "kept groaning, 'Oh, man, I messed up. I really messed up,'" one witness said.