Earlier today, four rabbis at a synagogue in Jerusalem were killed by a pair of Palestinian men armed with a pistol and meat cleavers. The attackers, who also injured eight others, were shot dead. According to BBC News, "It is the deadliest attack in six years in Jerusalem, which has seen weeks of unrest, partly fuelled by tension over a disputed holy site."

All of the rabbis killed have dual citizenship: One has British-Israeli citizenship, while other three have American-Israeli citizenship. The NY Times reports, "Witnesses and Israeli leaders were particularly horrified at the religious overtones of an attack on a synagogue that killed men in ritual garments and spilled blood on prayer books. 'To see Jews wearing tefillin and wrapped in the tallit lying in pools of blood, I wondered if I was imagining scenes from the Holocaust,' said Yehuda Meshi Zahav, the veteran leader of a religious emergency-response team, describing the straps and prayer shawls worn by the worshipers. 'It was a massacre of Jews at prayer.'"

One person inside the synagogue said, "I tried to escape. The man with the knife approached me. There was a chair and table between us... my prayer shawl got caught. I left it there and escaped."

President Obama condemned the attacks:

I strongly condemn today’s terrorist attack on worshipers at a synagogue in Jerusalem, which killed four innocent people, including U.S. citizens Aryeh Kupinsky, Cary William Levine, and Mosheh Twersky, and injured several more. There is and can be no justification for such attacks against innocent civilians. The thoughts and prayers of the American people are with the victims and families of all those who were killed and injured in this horrific attack and in other recent violence. At this sensitive moment in Jerusalem, it is all the more important for Israeli and Palestinian leaders and ordinary citizens to work cooperatively together to lower tensions, reject violence, and seek a path forward towards peace.

Israeli President Benjamin Netanyahu said Israel will "respond harshly," and blamed the attack on Hamas and Palestinian President Mahmoud Abbas. Abbas's office said, "The presidency condemns the attack on Jewish worshippers in their place of prayer and condemns the killing of civilians no matter who is doing it."

NYC Police Commissioner Bill Bratton said, "The NYPD is following developments in Jerusalem closely and working with the FBI Joint Terrorism Task Force to monitor any further developments. As of now, there is no specific credible threat to New York City. The NYPD has increased its attention to Synagogues and other symbolic locations around the city. Once again, we asked the public to be vigilant and if you see something, say something."

The attacks also elicited statements from Mayor Bill de Blasio, Governor Andrew Cuomo and other local officials:

"I am horrified and heartbroken by today’s terror attack in Jerusalem, which took the innocent lives of four people. My thoughts and prayers are with the victims’ families. New York City stands in solidarity with Israel at this difficult time, and we hope and pray for a peaceful and secure future for all of its people.‎ The NYPD is in close contact with its liaison post in Israel. We have increased our police presence at synagogues and other key locations around the city. As always, we ask New Yorkers to stay alert and immediately report any suspicious activity.”

- Mayor de Blasio

"I am deeply saddened to learn of this morning's horrific terror attack at a synagogue in Jerusalem. This attack was a deplorable act of evil that should be denounced as such by all - regardless of their political or religious beliefs. I want to reiterate that friends stand together in times of crisis. Today New York joins with all of Israel as they mourn those that were lost. We stand shoulder to shoulder with our Israeli friends." - Governor Cuomo

"The deplorable attack at a Jerusalem synagogue this morning is heartbreaking and should serve as a stark reminder of the existential threat faced by Israel. To attack and murder those who are worshipping, which is the ultimate act of peace, reveals the depth of the hatred, insanity and cowardice that defines terrorism. My thoughts and prayers are with the victims, their families, and all of Israel during this terrible time." - Assembly Speaker Sheldon Silver

"The brutal terrorist attack inside an Israeli synagogue is a despicable crime that has no place in any civilized society. A place of prayer is sacred and those who are ultimately responsible for this atrocity must be brought to justice. My thoughts are with the families of the victims, and I stand with them, along with the people of Israel and New York City, as we mourn this tragic, unspeakable loss." - NYC Comptroller Scott Stringer

"New Yorkers awoke today to the sickening news of a terrorist attack by Palestinians on a Jerusalem synagogue, resulting in the murder of four fathers--three Americans. The victims of this barbaric attack leave behind between them 20 children and 15 grandchildren. We join with leaders from around the world in condemning these murders as an intolerable depravity. Our thoughts and prayers are with the many who were injured, some of whom are fighting for their life." - The Jewish Caucus of the New York City Council and Speaker Melissa Mark-Viverito

"When I saw the news that four people were killed in a Jerusalem synagogue by Palestinians, I was in shock. Shocked that anyone could be so brutal to murder these worshipers during their prayers, shocked at the gruesome way they were executed, shocked at the celebrations in Gaza over the death of these innocents, shocked that this Palestinian terrorism violence continues to fester in Israel - a land of peace. The one thing that was not shocking is that the terrorist organization Hamas applauded these vicious murders. The international community must stand up and put an end to the blood-thirsty Hamas-led government of Gaza. Today's murders were more vicious than any killings to date by ISIS. ISIS, Hamas and their supporters are poisonous fruits from the very same Islamic terrorist tree that must be cut down." - City Council Member David Greenfield