On April 4, 2017, an airstrike killed more than 70 people in the town of Khan Sheikhoun in Syria.

What Syria said:

Syria claimed that no chemical weapons were used and that the videos showing the atrocities were fake.

What Russia said:

Russia claims that the strike hit only the Eastern outskirts of Khan Sheikhoun and between the times of 11:30 am and 12:30 pm EET (Eastern European Time).

However:

Eye-witness accounts, circumstantial evidence and videos from local journalists on the ground in Khan Sheikhoun tell a different story and highlight the inconsistencies (ranging from the time of the strike to the location) in the claims made by the Syrian and Russian governments.

Malachy Browne, Natalie Reneau and Mark Scheffler from the New York Times started to investigate, using satellite images, drone footage and eyewitness accounts:

In the case of Khan Sheikhoun, the most conclusive evidence was discovered by verifying the images and videos local journalists had captured.

Here are the open source tools that were used to verify the content:

• Google Earth and Google Maps to confirm the location of the strike.
• SunCalc to analyze shadows and direction of the sunlight to estimate timing of the strike.

Archival footage and reports from the Organization of Prohibition of Chemical Weapons to confirm Syria’s chemical weapons arsenal.