(CNN) When quadruple amputee and retired Marine Sgt. John Peck looks down at his new arms, he said, he's overcome with gratitude -- and vows that he will not take them for granted.

Peck soon will be able to use his arms to open heavy doors with circular handles, shake the hands of others and feel fiancée Jessica Paker's palm in his.

"That truly is a precious gift," Peck said, with a cross around his neck and tears in his eyes, at a news conference at Brigham and Women's Hospital in Boston on Wednesday.

The 31-year-old wounded veteran underwent a bilateral arm transplant at the hospital in August. A donor's two arms were surgically connected to Peck's body near his elbows, which doctors say will allow him to eventually feel, grasp and hold in a way that prosthetics couldn't.

"Would I ever imagine being here? No. I still to this day tell people about the arm transplant, and they say, 'Whoa, they can do that?' And I say, 'Yeah, they can do face, limbs,' " Peck said. "People think it's sci-fi."

A moment Peck will never forget

Peck's life completely changed in 2010. During his second tour of duty, he stepped on an improvised explosive device in Afghanistan, which triggered a blast that caused him to lose his arms and legs.

That wasn't the first time Peck was injured. He'd previously served a tour in Iraq, where he suffered a traumatic brain injury. He's the recipient of two Purple Hearts

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After losing his limbs, Peck was equipped with prosthetic arms and a wheelchair. However, in 2014, he was approved to undergo a double arm transplant, in which he would receive real arms from another young man -- a man who died.

"I will love him every day and will respect his life and this gift until the day I die," Peck said during Wednesday's conference, where he requested that an empty chair be placed next to him to represent and honor his donor.

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For Peck's surgery, a team of 12 surgeons worked nearly 14 hours to complete the transplant. The date and time of the surgery was not disclosed in order to protect the privacy of the donor's family, hospital officials said.

The procedure, which can be performed simultaneously on both arms, involved trimming the ends of the bones in Peck's arms and equipping them with plates, which were then connected to the bones in the donor arms.

Next, the surgeons connected the arteries and veins in Peck's arms to those in the donor's. As Peck's blood flowed into the donor arms, the donor hands turned pink, the doctors explained during the conference.

Once doctors repaired the muscles in Peck's arms, connected his nerves to those in the donor arms and sewed the connecting skin closed, the transplantation was complete.

Peck then went into recovery.

'Every day, it's a learning experience, and I love it'

Peck's surgery was led by Dr. Simon Talbot, director of the upper extremity transplant program at Brigham and Women's Hospital, and Dr. David Crandall, medical director of the Amputee Program at Spaulding Rehabilitation Network, where Peck has been undergoing outpatient recovery.

"In physical therapy, John has been working on his core and shoulder strengthening," Crandall said Wednesday. "John has been working on functional tasks of daily living including some self-dressing, grooming and teeth brushing."

But it will take about nine to 12 months for Peck to feel sensations, Talbot said.

"We've had patients who get their sensations back, and it comes back quite suddenly in the palm of the hand. Most patients say, 'One day I could suddenly feel a raindrop on my hand' or 'the pages of a book I'm turning,' " Talbot said. However, in some cases, sensation might fail to return.

Jeff Kepner, now 64, was the first patient to receive a double hand transplant in the United States, in 2009. One year after his surgery, he was still taking 50 pills a day and completing six hours of therapy every weekday to regain some function of his new hands.

"Unfortunately, things have not worked out as he had hoped," Kepner's family wrote on a GoFundMe page that was set up for his medical expenses.

However, Peck is hopeful for his future. The resident of Fredericksburg, Virginia, was the fourth bilateral transplant performed at Brigham and Women's Hospital.

"The pain has been tremendous at first. There was one night in the ICU, I believe it was the first night, that I had a bad night, and I wanted to call Dr. Talbot and tell him to come re-amputate my arms. It was a moment of weakness," Peck said of his recovery.

But now, "I'm learning how to transfer in and out of bed. I'm making really good milestones pretty fast," he said. "Every day, it's a learning experience, and I love it."

Chasing a culinary dream

Peck said he plans to pursue a culinary career and compete in the television series " Food Network Star " with his new arms, of which the upper left shows remnants of an old tattoo.

"My dream job since I was 12 was to be a chef, and because of my donor's gift, I actually have a fighting chance to do this," Peck said. "As a result of this surgery, I'll be able to pursue my dreams."

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Peck added that, for now, he has to be careful in the kitchen. Any injury, such as a cut or burn, could be devastating for his recovery.

"Last night, we were making shrimp and chorizo, and I was watching the pan to make sure we didn't burn anything, and I had to make sure my arm was away from the pan to make sure any oil or anything like that didn't get on it. ... I don't want to get any scarring or any cuts or anything like that. It takes extra thought," Peck said.

He looked down at his arms and added, "This gift, it's not going to go to waste at all."