A neighborly act turned into a near-death scare for one New Jersey man after a nail punctured his heart.

Dennis Hennis, of Vineland, N.J., was doing repair work on his neighbor's roof  last  Saturday when the safety feature on his nail gun jammed.  When Hennis went to unjam it, he pointed the gun in the wrong direction, shooting a three-and-a-half inch nail right into his chest.

"It felt like someone poking me in  the chest, like a tap," Hennis, 52, said to ABCNews.com today in a phone interview from his hospital room.  "There was no pain, actually, but a lot of shock.  I couldn't believe I had just done that."

The nail, doctors would later discover, had gone through Hennis' chest and right into the right side of his heart.  Unaware of the full extent of his injury, Hennis held on to the part of the nail still outside  his body as he waited with his son for paramedics to arrive.

From there began a coincidence of events that Hennis says kept him alive.

Fog in the area prevented paramedics from airlifting Hennis to Cooper University Hospital, where a team of trauma surgeons were waiting, so the rescuers drove Hennis the nearly 50-mile distance.

Just then, the fog began to lift, so paramedics returned to the local hospital to put Hennis into a helicopter.  On the way back to board the helicopter, Hennis went into cardiac arrest but  the local hospital was able to stabilize him.

Hennis was then airlifted to Cooper University Hospital but went into a second cardiac arrest just as he was met by a team of trauma and cardiac surgeons on the hospital's roof.

"They had to do CPR, which saved my life but ripped a bigger hole [in my heart]," Hennis said.  "But they were ready, and they got me into surgery."

The team of surgeons spent two hours operating to remove the nail and repair Hennis' heart.

"They had to stop my heart for 40 minutes for it to reset, and then they shocked it back on and I'm here," he said.  "I'm amazed."

Hennis said he was in and out of consciousness for three days and only fully "came back" on Tuesday.

"I lost three days. I didn't know," he said.  "I was drifting in and out.  I don't remember much."

Hennis credits his survival to fortunate  timing and the medical care he received at Cooper.

"He's very lucky. There are so many things that had to take place for him to be alive," Dr. Michael Rosenbloom, one of the surgeons at Cooper who treated Hennis, told  ABC affiliate station WPVI. "You're talking about a puncture wound to the heart."

Hennis is expected to make a full recovery and said he plans to return to his job as a builder, saying he would go "stir crazy" if he didn't.

He is expected to be released from the hospital on Sunday.

"I'm the luckiest man on earth right now," he said.  "A week prior, I had a grandson who was born on my birthday, so we're going to celebrate birthdays together from here on out."