Hours before the IDF notified the families of the 13 soldiers killed in Gaza early Sunday that their relatives had been slain, rumors of the deaths spread on the WhatsApp instant messaging app, which is how two of the bereaved families first heard of the loss of their loved ones.

A relative of one of the victims told Ynet that the victim’s brother, also an IDF soldier, was stationed outside Gaza when numerous people confronted him with the news that his brother had been killed. Only later did the army inform him officially and send him home, the report said.

“The circulation of these rumors is cruel, outrageous, and there must be an investigation into who’s spreading it,” he said.

Similarly, a second family received the news from WhatsApp, and was only formally notified hours later. One soldier’s best friends heard the tragic news via a text message as well, Channel 2 reported.

In other cases, the names of the soldiers circulated on WhatsApp turned out to be false, causing needless worry to various families.

One IDF soldier was said to be killed in Gaza, and his family plunged into mourning before learning that he was still alive, although he had been hospitalized in serious condition.

In other cases, Channel 2 reported, friends showed up at the doorstep of the parents of a Golani soldier, announcing that their son had been killed and comforting them ahead of receiving the dreaded IDF call, but the call never came, as the rumors turned out to be untrue.

Moshe Amar, whose brother Aharon was incorrectly identified on WhatsApp as having been killed in action, told Army Radio, “It’s a huge trauma. Until we received an official announcement, we didn’t know what to think.”

Users of the popular instant messaging platform, recently acquired by Facebook, have been criticized multiple times in the past month for spreading rumors relating to Israeli casualties and IDF operations.

Marissa Newman contributed to this report.