"I think you're a dummy that you didn't go for chief," his wife, Connie, said one afternoon, speaking of the LAPD.
But she could get him going by noting how his contemporaries Tom Reddin and Ed Davis had risen that far. Hadn't he done as well as them at the Academy, or as Tom Bradley, his 1940 classmate who become mayor? "Hell, no, higher!" O'Mara said, and she had him.
They all were part of a generation that was supposed to remake the LAPD. But the others had not been given the chore that had been an obsession in L.A. for a century, of protecting this paradise from the evil outsiders of the underworld. Every decade or so, another shadowy unit was formed to wage a war that left even its most celebrated foot soldiers tarnished in the end.
You could go back to Frank "Lefty" James, who was shot in 1913 trying to rid the city of "Eastern crooks" and then headed the Gun Squad targeting Prohibition racketeers. Lefty quit twice before he was shipped to the Valley and retired. Or Ed "Roughhouse" Brown, who sent Al Capone packing in 1927, only to be indicted for hanging around a bookie joint. "Somebody's gotta do the dirty work," O'Mara said, and for him it meant settling for being chief of the racetracks.
He taught his youngest to drive in Santa Anita's parking lot and she was a whiz. Everything came easy to Martha O'Mara, who went on to earn a doctorate in organizational behavior from Harvard, then taught in its business and design schools.
Maybe this was justice -- what became of him and the other Gangster Squad alums. Lindo "Jaco" Giacopuzzi became as rich as Wooters, with a shopping center on 10 acres. Jack Horrall became military liaison to the governor. And how about the judge? And him, O'Mara, with that brilliant daughter in Cambridge?
They all lived to see a crippled Mickey Cohen die in 1976, at 62, leaving an estate valued at $3,000.
In his own last years, O'Mara tended his rose garden in La Verne and fished the Sierra. He decided it was time to tell the tales of the Gangster Squad, though his wife thought it was a mistake. "You might put your foot in it," Connie O'Mara said.
He was the first to admit, "I'd go to jail today," but did she really think they'd haul him off for having taken the hit man Marshall Caifano up Coldwater Canyon for "a chat" in 1949?
"Oh, Daddy, don't go into that," she said.
"Leave it alone a minute, will you boss?" he said, convinced it was time to tell it all.
After she had her stroke, he lifted her in and out of bed, until he got weak from lymphoma. Then he picked their grave site in the San Gabriel Valley, on a slope with a tree to shade visitors. That's where his daughter read his eulogy after he died in June 2003, at 86. Martha O'Mara called it "A Good Life," and spoke of how he'd been "part of a team that really did keep organized crime out of Southern California."
You could make that case, for L.A. had never gone the way of Chicago or Philly, and its mob was derided now as a Mickey Mouse Mafia.
"To my father, there was good, there was evil," Martha O'Mara said. "He fought evil."
Then she looked around the cemetery. She noticed stones with disturbingly young faces etched into the marble. One to her folks' right showed a smiling fellow in a T-shirt, dead at 17. One down the lane showed an 18-year-old with a mustache. Then it hit her: "It's the gangbanger cemetery. These young men get blown away in the gang wars and then these families put these monuments up."
So many now died that way, their killings rarely made the news. The world never learned their nicknames as it had with Bugsy and Jimmy "the Weasel." Still, Mickey would've been proud of how they flaunted who they were on those stones.
It sure looked to Martha O'Mara as if her dad would be spending eternity alongside a new generation of gangsters. There was no escape, not for Jack O'Mara or for Los Angeles.
Times researcher Maloy Moore and former researcher Tracy Thomas contributed to this series.