Two Israelis - an Arab and a Jew - posted messages on Facebook saying they were going to kill someone on the other side of the Israeli-Palestinian conflict.
The two posters were real people with active Facebook pages, but the threat was part of an experiment conducted by an Israeli news station last week. The goal was to monitor the reactions of individuals and Israeli authorities who are tasked with keeping tabs on social-media posts they say might inspire terrorist attacks.
Critics in both communities say social media has served as a conduit for unstoppable deadly violence.
While the low-intensity Israeli-Palestinian conflict has been burning for decades, the platforms have given rise to individual extremists and lone-wolf attackers who are much more difficult to stop, officials say.
After posting that he had been inspired to kill Jews, Shadi Khalileh, the Arab citizen, received calls from concerned friends and family.
Israeli-Arab members of parliament, who heard about his post through word of mouth, even called to ask why he would post such a message, or whether his page had been hacked. Only 12 people "liked" his post.
The Jewish citizen, Daniel Levy, wrote that he had to seek revenge after a Palestinian killed a 13-year-old Jewish girl in her bed.
His post drew some 600 "likes," 25 shares and comments such as "I am proud of you" and "you are a king." One comment urged him to "please take the post down before you are arrested."
Israeli police questioned Khalileh about his post, and it took some work to convince them that it had all been an experiment. But Levy's post went undetected by the authorities, the news station said.
In neither case did Facebook flag the posts, which remained online until the station ended the experiment.
The failure of social-media platforms to take action against posts calling for the murder of Israelis or Palestinians, Jews or Arabs, has become a growing issue for those on both sides of this decades-old conflict.
Some Israelis say that Facebook posts in particular have inspired the renewed violence over the past eight months, during which 34 Israelis and two US citizens have been killed in stabbings, shootings and vehicular attacks by young, lone-wolf Palestinians.
They also say that some of the violence might have been prevented if the posts had been taken down or tracked. Authorities say that it is impossible for them to monitor millions of messages posted daily on social media but that they believe individual platforms have the capacity to track them.
Palestinians have also taken issue with social-media platforms, saying they incite violence and foster an Israeli discourse of hatred, racism and discriminatory attitudes against Palestinians.
"Palestinians are extremely worried of the current climate in Israel," said Saeb Erekat, secretary general of the Palestine Liberation Organization.
If Facebook has algorithms that can target individuals with advertising based on the content they post, then why can't it track and remove negative content?
"We are not ignorant, and we have seen the impact of such incitement in the form of settler terror and trigger-happy soldiers executing injured Palestinians in the streets of the occupied state of Palestine."
After the Israeli news experiment, Erekat released a statement pointing out the differences in how Israeli authorities treated the two participants.
Nearly 200 Palestinians have been killed in the wave of violence, which started on October 1. Israelis say the majority were killed carrying out attacks but in some cases have admitted to mistakenly killing innocent people. In other incidents, Israeli soldiers have been criticized for being heavy-handed.
Israel's minister of public security, Gilad Erdan, said Facebook and its creator, Mark Zuckerberg, should take responsibility for problematic content that appears on the network or at least work with Israeli law enforcement to curb violence and track down individuals who call for murder.
He said Facebook refuses to hand over IP addresses or identifying information of Palestinians who post in the West Bank, saying that the area is not under Israeli jurisdiction. Erdan also said that out of 74 requests by the Israelis for Facebook to remove problematic content, the company took down only 23 posts or pages.
There is no room for content that promotes violence, direct threats, terrorist or hate speeches on our platform.
"If Facebook has algorithms that can target individuals with advertising based on the content they post, then why can't it track and remove negative content?" Erdan said.
When asked by The Washington Post how it responds to Israeli government requests to improve its monitoring of problematic content and its failure to remove posts or pages that incite to murder, Facebook responded that it "regularly works with safety organizations and policymakers around the world, including Israel, to ensure that people know how to make a safe use of Facebook."
"There is no room for content that promotes violence, direct threats, terrorist or hate speeches on our platform," said a spokesman for the company.
On Monday, the relatives of five US citizens killed or injured in recent Palestinian attacks filed a lawsuit seeking more than $1 billion in damages from Facebook for knowingly providing services to the Palestinian group Hamas, which Israel and the United States have designated a terrorist organization.
Moments before fatally stabbing the Jewish girl, Hallel Ariel, in her bedroom in a West Bank settlement last month, the Palestinian attacker wrote on Facebook that he planned to "commit suicide or get killed carrying out an attack because it was his right."
He was shot dead at the scene.
Erdan and Justice Minister Ayelet Shaked presented legislation on Tuesday that would enable Israeli law enforcement to petition the courts to remove "illicit content that substantially endangers state security, the public or a private person."
It is unclear how Facebook would respond to any such order.
"I know this is not easy. There is the question of freedom of speech, but some red lines need to be defined when it comes to social media," Erdan said.