Sunday - a day that saw 13 soldiers killed in Gaza.
Determined to give Carmeli a well-attended funeral in Haifa on Monday night, some 20,000 Israelis from across the country turned out to pay tribute to a fighter whose lone soldier status won him much admiration. So many people attended, in fact, that there were heavy traffic jams in the city.
Israel calls them the lone soldiers: They are men and women in the prime of their lives who have left their parents and often comfortable lives behind in places like Sydney, London, Los Angeles and elsewhere to join the Israel Defense Forces, marching in the desert and taking up arms to defend the Jewish state.
"To the families of Max Steinberg and Sean Carmeli, I want to send my deepest and most heartfelt condolences," wrote the American-born former ambassador to the US Michael Oren on his Facebook page. "As someone who served as a lone soldier … I know only too well the enormous courage of these young people and their unswerving dedication to Israel. Though no words can even begin to compensate for your loss, just know that your sons' sacrifice has helped secure the lives of millions of Israelis. Their memories will be sacred forever."
There are about 2,000 lone soldiers currently serving in the military, said Marina Rozhansky, spokeswoman at the Israel Consul General in Los Angeles. Groups for families of lone soldiers have recently started in Los Angeles and other cities, providing a support network as the fighting intensifies.
For Jews who left Israel before the age of 15 or who never lived there, their service is voluntary. For many, it is a calling, a way to get back to their roots and unite the world's Jewish population. Some have dual citizenship. Others speak little to no Hebrew and have only recently been to Israel.
Max Steinberg, 24, who grew up in Southern California's San Fernando Valley, joined six months after he visited Israel for the first time on a Birthright Israel trip with his younger brother and sister in June 2012, said his sibling Jake, who spoke to The Associated Press hours after learning his brother, a sharpshooter in the Golani Brigade, was among the 13 IDF soldiers and scores of Palestinians over the weekend who died during the first major ground battle in two weeks of fighting between Israel and Hamas.
"He got there and felt a connection to Israel, saw that as a place he could live and be successful, and he went for it," Jake Steinberg said.
Nissim Sean Carmeli, 21, the second American killed, was from South Padre Island, Texas, and he felt that same strong connection to the country he had only moved to four years ago.
Rabbi Asher Hecht of Chabad of the Rio Grande Valley, who is a family friend, said Carmeli joined the IDF about four years ago.
"He had great energy, yet had a kind and gentle soul," Hecht said.
Steinberg had been living in Be'er Sheva. He visited Israel for the first time on a Birthright Israel trip in June 2012, his father, Stuart, said. When he returned, he told his parents that he was planning to return and join the IDF. He made good on that promise less than six months later.
"He was completely dedicated and committed to serving the country of Israel," Stuart Steinberg said. "He was focused, he was clear in what the mission was, and he was dedicated to the work he needed to be doing."
Stuart Steinberg last spoke to his son at early Saturday morning California time, hours before his death. Max called his father to tell him that his group had been wounded when two of their tanks collided. They had to return to Israel for treatment. Some soldiers had broken bones, and Max Steinberg had sprained his back, his father said.
"He called me up at 4 am that morning and said he'd be returning to Gaza, back to combat, to be with his friends," Steinberg said.
Mike Fishbein, who grew up in Los Angeles, said he felt like he was missing a connection to his Jewish identity in California. He spent a year volunteering and studying in Israel, but that experience only deepened his desire to do more.
"I believe in that country. I believe in the Jewish people and the country's reason to exist, so I thought I can't just go back home to Los Angeles," said Fishbein, who served about two years with the Israel Defense Forces starting in 2009.
After Fishbein enlisted, he spent 30 days learning Hebrew along with more than two dozen others from Panama, South Africa, Australia and other nations. He then went through basic training, which included a 40-mile nighttime march through the desert. He lived for almost four months inside a worn tent from the Vietnam War era.
Israeli troops wondered why he would leave the palm trees and beaches they had seen in movies.
"They didn't understand why a kid from Hollywood was there," he said. "But after you stuck around, they would respect you and understand (that) we're here together to try and protect the same thing."
When Fishbein heard of the two Americans killed, it touched him deeply, he said. He has struggled to post on his Facebook page his emotions or even give an explanation to his friends in California as to why he felt the need to serve. He never wanted to join the US armed forces, Fishbein said.
For the 25-year-old commercial production assistant, serving in the Israel Defense Forces was the culmination of milestones in his life, he said. In ninth grade, he accompanied his father with a documentary crew filming the unearthing of Jewish artefacts in a once largely Jewish town in Poland that was destroyed in the Holocaust.
"That was a surreal experience for a ninth-grade kid to go through, but it set me up to go to Israel and serve," he said. "Every lone soldier has had something similar."
Josh Reznick, 24, who works for a real estate investment firm in Baltimore, briefly considered joining the US military, but after living on a kibbutz for a year, he realized his calling. He served in the same unit as the two Americans killed during the weekend. He did not know either of them, but he did know one of the fallen Israeli troops.
Reznick believes the Steinberg and Carmeli will be "shining examples" for other lone soldiers. He was inspired by Michael Levin, a lone soldier from Pennsylvania killed fighting for Israel in 2006. He visited his grave site in Israel, where his tombstone is covered in Phillies baseball hats and Eagles jerseys.
"It's very nice living in America and everything is fine. But I'm sure people right before WWII felt the same way about living in Germany," he said. "If only there had been a place to run to for the Jews. That's why it's important to keep Israel, a Jewish nation, alive."
Isaac Cohen, 18, of Silver Spring, Maryland, starts this month at an Israeli military prep school before joining the army next year. He isn't deterred by the recent violence.
"They teach you how to survive in Israel," said Cohen, who lived there for six years. "You kind of have to survive there. I feel a lot stronger when I'm there."