Most reports indicate  that the plane was shot down by a missile approximately 50km from the Russia-Ukraine border. The Ukraine government is accusing pro-Russian insurgents of using  a BUK surface-to-air missile system to shoot down the plane but rebel leaders have denied  this.
This infographic shows the flight path and crash site of MH17:
Infographic: Crashsite Map incl. MH17 Flight Path – pic.twitter.com/JkPwUJAv8u 
— Florian Witulski (@vaitor) July 18, 2014 
Malaysian Prime Minister Najib Razak assured  his constituents that those who shot down the plane will be brought to justice:
This is a tragic day, in what has already been a tragic year, for Malaysia.
If it transpires that the plane was indeed shot down, we insist that the perpetrators must swiftly be brought to justice.
The flight’s passengers and crew came from many different countries.
But today, regardless of nationality, we are all united in grief.
He also clarified that the aircraft’s flight route, even if it passed directly above a conflict zone, was declared safe by the International Civil Aviation Organisation.
The MH17  crash was the second time that a Malaysian Airlines Boeing 777-200 aircraft went down this year. On March 8, a Malaysian Airlines MH370 plane carrying 237 people went missing  just an hour after it left Kuala Lumpur during its flight to Beijing. The MH370 plane and its passengers have yet to be found .
A daughter of an MH370 flight attendant tweeted her message of support to the families and friends of MH17 passengers:
As the family member of the crew MH370, and on behalf of all them, we pray for MH17. Stay strong dear families. #PrayForMH17 
— Maira E. (@Gorgxous_) July 17, 2014 
Josie Fernandez of Transparency International Malaysia urged a complete probe  of the incident:
What has happened is unprecedented – Malaysia is the only country where the same carrier, the same type of planes have been involved in tragedies with loss of many lives within months. MH370 has not been found.
Malaysia must demand for international action on this unprecedented tragedy. This is a passenger plane. We are not at war with any nations.
Writing for The Ant Daily, Alyaa Alhadjri described the shooting down of MH17 as a ‘mass murder’ :
Why are commercial passenger jets still flying over a conflict area where airplanes have been shot down and warned to steer clear of the airspace.
Whatever the causes for another MAS Boeing 777 for going down a second time in 133 days, losing 537 people in two air disasters does not help lift passengers’ confidence in the national airline.
As Malaysia grieves  over another tragic crash, it seems inevitable that many citizens will again press the government to explain the mysterious disappearance of MH370.