DHAKA, Bangladesh — Bangladesh’s capital city reeled in shock on Sunday as clues began to flood social media about the privileged backgrounds of the half-dozen attackers believed to have butchered 20 patrons of a restaurant during a bloody siege here late last week.

The six attackers were killed when the army stormed the Holey Artisan Bakery to end an 11-hour siege early Saturday.

The police declined to name the young men because nobody had shown up as of Sunday night to identify their bodies, but friends and relatives recognized photographs that were posted on a messaging app by the Islamic State, along with praise for the violence.

The men, all in their late teens or early 20s, were products of Bangladesh’s elite, several having attended one of the country’s top English-medium private schools as well as universities both in the country and abroad.