Skarlatos, who was one of the three Americans who took down a terrorist on a train to Paris, was enrolled at Umpqua Community College and would have been in class had he not taken part in the dancing show.
"Once I found out about the shooting, I just started calling all my friends and family," he said during the show. "I felt totally hopeless. Like there was nothing I could do. I just felt like I needed to get home as fast as I could."
He raced to the city, where he attended a candlelight vigil for the victims.
He told DWTS: "Being here under these circumstances, it just doesn't feel the same. This isn't the quiet town that I left. It's honestly the strangest emotions I've felt. Even the train made more sense than this does."
He dedicated his dance on Monday to those affected by the tragedy.
Alek spoke with INSIDE EDITION backstage after the performance.
He said: “When I heard the news I was shocked.”
Alek performed a Pasodoble with his partner Lindsay Arnold.
“He really nailed it considering what he's been going through,” she said.
Nine people were killed in the shooting in Roseburg last Thursday. The gunman is then believed to have taken his own life.