Jake Gyllenhaal (left) stars as Lou Bloom, a TV news stringer who chases after crime and accident footage, in ìNightcrawler.'

Overstatement is the sincerest form of outrage in “Nightcrawler,” an impressive directorial debut from screenwriter Dan Gilroy that, true to its title, creeps under the viewer’s skin much like the predatory title character, who restlessly cruises through this modern-day media allegory like Travis Bickle’s long-lost, hyper-wired West Coast cousin.

Lou Bloom is a young man on the make, an ambitious, mercenary margin-dweller who scrapes by as a petty criminal and listens to business self-help tapes in hopes of finally scoring big-time. When Lou discovers there’s a decent living in filming car accidents, fires and crime scenes for local television news spots, he immediately sees the chance he’s been chasing: What better fit for a resourceful if unsavory scavenger like him than to throw in with the bottom feeders who supply tabloid infotainment with its daily supply of murder, mayhem and malfeasance?

Soon, Lou is trolling Los Angeles streets with a police scanner and a cheap digital camera, cutting deals with a desperate news producer named Nina (Rene Russo) and leading viewers on a Dante-like journey through a news culture where violence, gore and racially charged crime reporting have become the bread and circuses of an image- and anxiety-driven era. (If it bleeds, it leads, Nina tells Lou, especially if the one bleeding is a telegenic white woman from an upscale neighborhood — extra points for paranoia if she’s the victim of a black perpetrator.)

“Nightcrawler,” which Gilroy also wrote, shares a lineage with some great American films, including “Network,” Michael Mann’s “Collateral” and the signature works of Martin Scorsese, including “Taxi Driver” and “The King of Comedy.” Channeled by an almost unrecognizable Jake Gyllenhaal — here alarmingly gaunt, wild-eyed, rictus-grinning, his voice a high-pitched, reedy patter — Lou is the jittery, jaundiced avatar of the fatal collision of burgeoning technology, dying legacy media and a society in cultural and economic extremis.

The film derives cynical humor from Lou’s twisted rhetoric of bargaining positions and projected growth curves when talking about his seedy vocation. (He’s meant to be a cautionary proxy for a generation of millennials facing down foreshortened career prospects and distorted notions of privacy and personal ethics.) Russo’s Nina Romina is a down-market version of Faye Dunaway’s Diana Christensen in “Network,” neurotically aware of her own looming obsolescence and the need for her dowdy nighttime newscast to compete with the likes of TMZ and its devil spawn of amateur paparazzi and freelance opportunists.

There are moments when “Nightcrawler” becomes too strident for its own good, and the plot ultimately goes into its own sensationalistic, far-fetched territory that compromises Gilroy’s impressive tonal and visual control. The film has a sulfuric, Dostoyevskian quality — and sick sense of humor — that captures the muted aquarium that Los Angeles becomes at night, a spell that’s broken once plot overtakes mood.

Still, Gyllenhaal is a queasily mesmerizing Raskolnikov, his stringy, fast-talking hustler slithering through the fetid nightscape like a figure possessed. And it’s fantastic to see Russo — who happens to be Gilroy’s wife — working again; with luck, the hardened fragility she brings to Nina will remind non-relatives in Hollywood that she’s still a stunning, steady presence on screen.

“Nightcrawler’s” most salient — and sobering — point isn’t that soldiers of misfortune such as Lou exist, but the degree to which mainstream media has jumped into bed with them, pandering to the public’s shameful appetites (suggesting one more movie for the shared-DNA list: “Gone Girl”). The film ultimately turns its rancid gaze on the audience itself, questioning the bull market for lurid true-crime tales, even as crime rates are actually going down.”Is that blood on your shirt?” Nina asks Lou at one point. Yes, and it’s on his hands — and hers, and everyone else’s — too.