Original sentence: Another stampede occurred in September 2015, when at least 717 people were killed and 863 others were injured at Mina, just outside the holy city.These two factors are felt to be most responsible for a stampede during the Hajj of 2006 which killed at least 346 pilgrims and injured at least 289 more
Edited sentence: Another more severe and tragic stampede occurred in September 2015, when at least 717 people were killed and 863 others were injured at Mina, just outside the holy city.These two factors are felt to be most responsible for a recent tragedy during the Hajj of 2006, in which a stampede killed at least 346 pilgrims and injured at least 289 more