On Monday, hundreds of Shaar's fellow students marched to the Starco building, outside of which the bombing took place. They held signs saying "We are all Mohammed," waved the Lebanese flag and left flowers.
The powerful car bomb targeted Mohammed Chatah, a former finance minister critical of Syria and Hezbollah. Chatah's allies in a mainly Sunni political coalition backed by the West quickly pointed the finger at the Shiite Hezbollah guerrilla group, which denied the accusations.
But the blast, on a main avenue of the ritzy downtown shopping district, killed not only Chatah and his driver but also five passers-by — including Shaar.
Friends said Shaar was out in downtown celebrating the end of the school semester, having coffee with his three friends at a Starbucks. They then strolled through downtown to the Starco building, a complex of offices and shops. There, they took that last selfie. Moments later, the district was shaken by the blast, which sent a plume of black smoke over the area — and Shaar fell with a bleeding shrapnel wound in the head.
At his funeral on Sunday, sectarian anger bubbled up, with some mourners chanting anti-Shiite slogans.
But more prevalent was anger over being caught in the crossfire as powerful factions — whoever they may be — fight out their political differences. Shaar, a Sunni, wasn't political or particularly religious, those who knew him said. Several hundred emerged for his funeral, and tens gathered outside, some holding signs protesting the deaths of civilians.
"Every one of us imagined ourselves in that place," activist Mohammed Estateyeh said outside the Khashakhgi mosque in the Sunni-dominated Beirut neighborhood of Qasqas after Shaar's burial. "The picture of Mohammed lying on the ground — and the picture just before the explosion — they were four guys who were just hanging out."
Estateyeh, of the Muslim Students League in Beirut, printed black-white-and-yellow posters of Shaar, with the Arabic-language hashtag slogan scrawled underneath: "(hash)We—are—not—numbers."
The slogan caught on online, with some people posting pictures of themselves holding it on Facebook. Montages of Shaar's life-then-death photos circulated widely on Facebook and Twitter.
"Kill the person you want to kill — that's why they invented guns," Shaar's former geography teacher Dalal Batrawi wept at the funeral. "If that's the path you want to take, leave the rest of us alone."
Earlier Sunday, at a memorial ceremony carried live on Lebanese television, Shaar's teachers and students from the private Hariri High School — named after an assassinated Sunni former prime minister — described the teen as a bright, goofy student who loved basketball, lasagna and Harry Potter. He often bought cookies, croissants and milkshakes for his friends. Friends recalled him chatting with them at 5 a.m. on the instant-message system "Whatsapp."
"You know what sucks?" his friend Rahaf Jammal said at the memorial, speaking in English. "It's the fact that he didn't finish the book I got him for his birthday. He didn't finish Harry Potter (movies) because he kept asking me to watch it with him."
"It's the fact he had his whole future planned out and he couldn't accomplish anything, because of this stupid, cruel and crappy country."
The grief over Shaar is given greater resonance by the fears among Lebanese that they are lurching back into the abyss, still battered from their own 15-year war, which ended in 1990. That civil war was partly ignited by sectarian tensions among Lebanon's Shiite, Sunni, Christian and Druse minorities.
Sunni-Shiite tensions began growing after a powerful car bomb in 2005 killed the former prime minister, Rafik Hariri, who called for an end to neighboring Syria's domination of the country and criticized Syria's ally Hezbollah. Hariri's assassination was followed by over a dozen other assassinations of anti-Syrian figures. His allies blame Syria and Hezbollah for the killings; both deny involvement.