The pulsating shimmer of Los Angeles at night can seem either like a dream-scape fantasia or a topography of nightmares. In the new film “Nightcrawler,” it is both, a land of opportunity and madness and left in some measure for the viewer to unravel.

The directing debut for Dan Gilroy, who also wrote the screenplay, the film enters the world of nighttime crime-scene videographers as a jumping-off point to explore contemporary media culture, self-created personalities in the Internet age and the boundaries of personal ambition. The film had its world premiere as part of the Toronto International Film Festival, will have its U.S. premiere at the Fantastic Fest in Austin, Texas, and open in theaters on Oct. 31.

As the film opens, Lou Bloom (Jake Gyllenhaal in a transformative performance) is adrift on the fringes of society, stealing scrap to sell at salvage yards. After seeing a freelance video news team swoop in during the aftermath of a freeway car crash, he sets a new goal for himself. The right person finding the right opportunity that fits his specific pathology just so, Bloom makes a quick study of his new profession, while encountering a more established competitor (Bill Paxton), a television news producer (Rene Russo) desperate to make a mark and a hapless tag-along assistant (Riz Ahmed). Bloom’s rise comes with no minor cost and a small body count.

The enigmatic character of Bloom, stubborn, self-taught, self-made and possibly sociopathic, and personified by Gyllenhaal’s full-throttle performance, makes “Nightcrawler” many things at once. It is a character study, a disturbing look at the impact of media and culture, a fascinating glimpse into the nocturnal life of Los Angeles and an unpredictable, pulse-quickening thriller.

“I didn’t look at Lou as a deranged, damaged person,” said Gilroy. “I really wanted to look at a person who doesn’t have the programming and support from childhood and has limited tools to survive. To me, the through-line of the character was somebody trying to survive in today’s world.”

Gilroy started with an interest in the crime photographer of the 1930s and ’40s known as Weegee and then began to learn of the contemporary world of news videographers who refer to themselves as “nightcrawlers.” Connecting these together was a long fascination with what he called the “kabuki theater” of local L.A. news.

Jake Gyllenhaal stars in “Nightcrawler,” a dark moody vision of Los Angeles outside of the golden streets of Hollywood.