In the 116th Annual running of the Boston Marathon, a huge happening has taken hold.

Geoffrey Mutai, the world's number-one marathoner has pulled out of the race due to cramps, according to Ryan Hudson via twitter.

The 30-year-old was in the lead before having to withdraw.

The Kenya native is the defending Boston Marathon champion after winning it in 2011 with a time of 2:03:02, a course record.

He also won the New York City Marathon later in the same year in 2:05:05, another record for the event.

Mutai was a favorite coming into the race, so this is certainly a stunning and event-altering injury. It's more than fair to wonder how the unusual heat for this time of year is effecting Mutai and the cramps he's experiencing.

It's too bad his journey had to come to an end like this, but thus is the life of a marathon runner.

For more on the Boston Marathon, be sure to check out our StoryStream throughout the day.