An Israeli air strike killed Luay Kaheel, 16 and Amir al-Nimra, 15, while they were playing on a rooftop of a building.

Umm Luay zooms in on a photograph on her mobile phone and kisses the screen, again and again.

In the photo, her son, Luay Kaheel, is seen smiling alongside his friend, Amir al-Nimra. The two teenagers, 16 and 15 respectively, died on Saturday minutes after an Israeli air raid hit the rooftop of a building in Gaza where they were playing.

“I heard an explosion, and instinctively knew that something had happened to my son,” Umm Luay, 33, told Al Jazeera on Sunday, surrounded by a group of women sitting inside her home in Gaza.

The young mother had just arrived home when the air raid struck the building in al-Kateeba square, located next to a park frequented by Palestinian families during the summer months.

“I first heard that Amir was killed, and it was then that I knew,” she said. “I ran to the hospital and began looking for my son, frantically.”

Upon her arrival at al-Shifa hospital, a group of men immediately broke the news to Umm Luay – her son had also lost his life.

On Saturday, the Israeli army launched a series of air raids on what it said were Hamas positions inside Gaza. Apart from the two boys killed, at least 30 Palestinians were also wounded in the attacks.

It was the most violent daylight assault on the besieged enclave since the 2014 war when at least 2,251 Palestinians, most of whom civilians, were killed. At least 66 Israeli soldiers and six civilians were also killed at the time.

Hamas said on Saturday it launched dozens of rockets and mortars in response to the Israeli air raids. At least four Israelis were lightly wounded.

The father of Amir al-Nimra mourns after the funeral of his son [Hosam Salem/Al Jazeera]

‘Never thought I’d lose one of my kids’

Both born in 2003, Luay and Amir were inseparable. “Like twin brothers”, their mothers said.

The two boys grew up in the same street in central Gaza. They were classmates since pre-school and would walk together to school every day.

“He was very smart,” Umm Luay said of her son, her voice breaking. She had always hoped Luay, who enjoyed reading, would grow up to pursue a university degree abroad so he would have access to “better opportunities”.

“I treated him sometimes like he was 10 years older,” she added of Luay, the eldest of six children.

When not in school, the pair would also spend most of their spare time together, often visiting the park near al-Kateeba square to play football.

Passionate about the sport, the boys followed the 2018 World Cup tournament closely and would always compare themselves to famous players.

“My son left the house with a football, not a weapon,” Umm Luay said.

Devastating siege

Like many Palestinians in the Gaza Strip, Luay and Amir had lived most of their formative years under a crippling Israeli and Egyptian-imposed blockade, now in its 12th year.

The siege has devastated the coastal enclave’s economy, severely restricting food entry and access to basic services. Home to more than two million people, Gaza has been dubbed “the world’s largest open-air prison”, and in the past 12 years, it has witnessed three Israeli assaults.

“A day before he was killed … he told me how he felt suffocated by the reality on the ground,” Umm Luay recalled.

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Since March 30, people in the Gaza Strip have been protesting against the blockade and for Palestinians’ right to return to the homes from which they were expelled from in 1948. More than 130 people have been killed by Israeli gunfire during the popular Great March of Return rallies alongside the fence with Israel.

Last week, Israel sealed off Karam Abu Salem, Gaza’s only commercial border crossing, saying it was in retaliation to Palestinians setting fire to Israeli land. The crossing is the primary passageway used for the transportation of necessities to the enclave’s residents, including construction materials needed to rebuild much of the city’s devastated infrastructure.

Ayed Abu Qtaish, a director with the Line from Defence for Children International – Palestine NGO, told Al Jazeera the number of children killed by Israeli forces in the Gaza Strip since the beginning of 2018 stands at 25.

Umm Luay said she was always aware of the risks of raising her children in a place riddled with so much trauma and violence, but she did not expect something like this to happen.

“I never thought I’d lose one of my kids,” she said, crying.

Relatives grieve after the death of the two teenage boys [Hosam Salem/Al Jazeera]

‘ I can’t fathom it’

While Luay suffered a hit in the head and in the back, Amir’s entire body was punctured with shrapnel wounds.

Medics at the scene found Amir’s mobile phone nearby and gave it to his relatives.

Scrolling through the device, Amir’s mother, Maysoon al-Nimra, looked at the last photograph of her son, taken by himself at the top of the semi-abandoned building before the air raid.

“When the attacks happened, like any mother I gathered my children around me, but Amir was still not home,” she recalled.

Moments later, a relative came running with a photo they had received from someone at the hospital. It showed a boy in a green shirt that was covered in blood.

Maysoon realised the shirt belonged to Amir and rushed to the hospital.

After being told that it was only Luay who had been killed, Maysoon suspected the hospital staff were only trying to console her before slowly letting her know the truth about her son.

She quickly made her way to the hospital morgue instead, and found her son wrapped in several layers of white sheets.

“I started shaking him, trying to wake him up. I felt like I was in a dream.

“I can’t fathom it. I spent the night just staring at one picture of him, smiling and the other picture of him, blood coming out of his head,” she said.

“How did this happen? How could it happen? There’s a massive hole in our house now and it will never be filled.”