After Israel suffered one of the most deadly and devastating terrorist attacks last weekend, entrepreneur Noy Leyb said he knew what he had to do.

Leyb said he immediately packed his gear and a few belongings, headed to the airport from his New York home and flew to Israel to take part in the military's response against Hamas.

"There was no way I was going to stay in New York and try and hope or pray from the side," Leyb told "Nightline."

On ABC News Live at 8:30 p.m. on Thursday, Oct. 12, ABC News' James Longman, Matt Gutman and Ian Pannell look at the horrendous toll from Hamas’ massacre, the Israelis and Palestinians caught in the middle and what comes next.

He is one of the roughly 360,000 Israeli reservists from around the world who have answered their country's call to fight.

And while the terrorist attack and escalated conflict have spurred those soldiers into action, it has also left their families, some of whom are thousands of miles away, with despair over what's to come.

Even with 14 years of training, Leyb said he doesn't know how prepared he can be to respond to the Hamas attack that left over 1,200 people dead, thousands more injured and several people kidnapped.

However, he said he is mentally and physically ready to do his duty.

"We're going to go in and are going to ensure that we only come out when every single one of the last Hamas terrorists is gone," Leyb said.

Leyb explained it was tough to say goodbye to his parents, who have three children fighting for Israel.

"I don't know if I'll come back. No one wants to face that reality," he said.

Natalie, a 30-year-old New York resident who asked "Nightline" not to disclose her full name, said she is feeling that fear too. Her husband Edo, an Israeli national, was in Israel last week for a wedding and volunteered in the reserves.

The situation is personal for the couple, who have only been married for a year, as both of their grandparents were Holocaust survivors, Natalie said.

"I'm so proud of him and every single one of these people who are the front lines who are helping in the background, doing everything they can to protect us, to protect our country…and especially for Edo and I [to] do what our grandparents couldn't," she said.

Scott Lawrence, an Israeli-American chiropractor, who has four children now serving in the IDF, says his oldest two children dropped everything to fly from Spain and San Francisco to answer the call to fight for their country.

"We are painfully proud that our children have a higher purpose in themselves," Lawrence told "Nightline."

While the situation is still fluid and Israeli officials haven't ruled out a ground war, Leyb said he and his comrades are trying to push aside their fears and do what is right.

"You have people with families at homes, and no one wants to be here," he said. "But it's just our duty."