Anton Yelchin, the Russian-born actor who played Chekov in the new Star Trek films, has been killed by his own car at his home in Los Angeles, police say.
It struck him after rolling backwards down the steep drive at his Studio City home, pinning him against a brick postbox pillar and a security fence.
He died shortly after 01:00 (08:00 GMT) on Sunday.
Yelchin, 27, also appeared in such films as Like Crazy (2011) and Green Room (2015).
Yelchin played Pavel Chekov, the role originally made famous by Walter Koenig (now 79), in the films Star Trek (2009) and Star Trek Into Darkness (2013).
A third film with him in the role, Star Trek Beyond, is due for release next month.
'This impossible time of grief'
News of his death led Twitter trends in Los Angeles and beyond on Sunday.
Zachary Quinto, who plays Spock in the series, wrote on Instagram: "our dear friend.
our comrade. our anton.
"One of the most open and intellectually curious people i have ever had the pleasure to know. so enormously talented and generous of heart. wise beyond his years. and gone before his time. all love and strength to his family at this impossible time of grief."
Fellow Star Trek actor John Cho, who plays Sulu in the series, tweeted, "I loved Anton Yelchin so much. He was a true artist — curious, beautiful, courageous. He was a great pal and a great son. I'm in ruins."
The official @StarTrek Twitter account marked his death with a simple, sombre image.
An only child, he was born to professional figure skaters in Leningrad (now St Petersburg), who moved to the US when he was still a baby.
Los Angeles police officer Jenny Hosier said Yelchin had just got out of the vehicle when it rolled back.
He had been on his way to meet friends for a rehearsal, she added.
When he did not arrive, the group came to his home and found him dead, the police spokeswoman said.
The actor's publicist, Jennifer Allen, confirmed the actor's death and said his family had requested privacy.