The clock stopped at 2.14.74 and Arop was really worn out in the last 50 meters and stumbled a bit on the edge where the green lights inexorably disappeared from him at the Boston gala.
The 25-year-old was in the record time when he passed 800 meters in 1.46.69 with one lap to go.
The world record is held by Ayanleh Souleiman, Djibouti, at 2.14.20 from the Avicii Arena in Stockholm from the winter of 2016.
In 800 meters, Swedish Wilma Nielsen set a personal record with 2.02.91. She was seventh in the close race won by Sammy Watson in 2.01.20