‘Maze Runner’ Director Says Injured Star Dylan O’Brien Is 'One Tough Cookie'

In a handwritten letter, Wes Ball called O'Brien "one tough cookie."

— -- "The Maze Runner" director said he feels guilty after the star of the film series, Dylan O'Brien, was injured on set Thursday.

"Well, it's been a whirlwind of emotions these past few days," Wes Ball wrote in handwritten note, which he tweeted Saturday.

"I've been overwhelmed with feelings of anger and sadness and guilt. But, ultimately I find myself left with a deep love and respect for Dylan," he continued. "He is one tough cookie."

"I'm sorry for the grief this accident has caused his friends and family as well as my wonderful cast and crew," Ball, 35, continued. "It's scary seeing your friend get hurt, but fortunately, Dylan is going to be just fine. After a few weeks of rest and recovery he'll be back up and running to finish our adventure together."

Ball closed his note with, "All the best."

O'Brien, 24, has been in Canada, shooting "The Maze Runner: The Death Cure," the final installment in the three-part series. He suffered multiple injuries on set due to an accident, his rep confirmed to ABC News. O'Brien received medical attention at a local hospital, she added.