Terror Train Hero Alek Skarlatos -- Oregon Campus Shooting Hits Close to Home ... Bolts Out of 'DWTS' Rehearsal

Terror train hero Alek Skarlatos was rehearsing for "Dancing with the Stars" when he got gut-wrenching news -- his college was under attack from the shooter who killed 10 people on Thursday.

Sources at 'DWTS' tell us Skarlatos was in the middle of rehearsals with Lindsay Arnold when he got a phone call about the tragic shooting at Umpqua Community College. In addition to the 10 fatalities, police say the shooter injured at least 7 others.

We're told Alek immediately left the studio when he got the news, and was making calls back home to make sure his friends were safe.

Skarlatos, who's an Army National Guardsman in Oregon, is studying at Umpqua CC for a career in law enforcement.

Shortly after leaving the studio, he tweeted, "Everyone send prayers out to ucc."