''I blew up a week ago,'' recalls Denis Leary. ''It was about a charity event and somebody had made a promise and, you know...'' As he sits in the lobby of Manhattan's Mercer Hotel, the Rescue Me star's face curdles in self-disgust. ''I flew into a rage,'' he explains. ''It was really f---ing stupid.''

In short order the stand-up comic and actor also takes caustic aim at the failings of Ben Affleck (''He went the big Hollywood movie route and ended up nowhere''), George W. Bush (''I could make a documentary about how much of a moron he is, but I don't want to put that much work into it''), and the late emergency drama Third Watch (''s---''). But today Leary seems, rather redeemingly, to prefer picking at his own flaws. ''I'm 48 years old and should know better,'' he continues about his explosion. ''But I have a black Irish temper.''

To be sure, that Emerald Isle anger figures heavily in Leary's latest, greatest creation, FX's Rescue Me — a show that blurs the line between heart-wrenching tragedy and gut-busting hilarity. Leary got the initial inspiration for the series, which tracks a New York fire crew in the aftermath of 9/11, after a cousin died fighting a blaze in their hometown of Worcester, Mass., in 1999. From the start he's delighted in portraying its subjects warts and all. But in its third season, Leary is clearly singling out his foulmouthed, rage-filled, self-flagellating alter ego, Tommy Gavin, for ever more darkly absurd and just plain dark treatment.

Things crossed the line in episode 4 (which aired June 20) when Gavin raped his estranged wife, who seemed to at least somewhat enjoy the experience. Shockingly brutal yet simultaneously played for laughs (the act happens amid a discussion about a chaise longue), the sequence is highly controversial, with the Chicago Tribune, for one, calling it ''a sickening new low.'' But at least prior to the furor, Leary beamed with pride: ''I think it's one of the best things we've ever done. It's really remarkable in terms of the emotion and temperament.'' His point: Where's it written that a hero has to be likable? ''In a fire, I would want to be real close to him,'' he says of Tommy. ''In real life, I wouldn't want to sleep over at his house.''

Leary's unsparing portrayal of blue-collar life is rooted in his own. ''When I was 6, the guy who was president — and who was a f---ing saint in the apartment I grew up in because he was Irish — gets his head blown off,'' he explains. ''I think we were just dark by nature, that generation.'' Leary himself was destined to be a fireman until a nun persuaded him to appear in a school play and later to apply to Boston's Emerson College for drama. After graduating, Leary wandered into a talent night at a Chinese restaurant hosted by his future Rescue Mecostar Lenny Clarke, who was offering $25 to anyone willing to go on stage. Needing the money, Leary stepped up — and bombed. ''He stunk the joint out,'' recalls Clarke. ''But even if he wasn't killing, he didn't give a s---. He was doing it his way.''