LAS VEGAS — In nearly 30 years with the Las Vegas police, Joseph Lombardo has helped defuse an armed standoff between federal agents and local ranchers, struggled to contain a spike in homicides and defended his officers against accusations of using excessive force against a professional football player.

But nothing could have fully prepared him for last week.

Since a gunman smashed out windows in a casino hotel suite on Oct. 1 and rained bullets on a country music festival, killing 58 people and wounding hundreds more, Sheriff Lombardo has found himself in charge of one of the most frustrating criminal investigations in memory: a mass shooting by a man who seems to have left no public accounting for his actions.

So far, Sheriff Lombardo, a plain-spoken man whose persona contrasts sharply with his city of flashing billboards and jangling slot machines, has not been able to uncover a motive for the shooting. And he has wondered aloud whether something — anything — might have prevented the bloodshed.

“We are always preaching, ‘If you see something, say something,’ ” Sheriff Lombardo told The New York Times last week, in one of his first interviews since the shooting. “So how did we miss this, in the see-something-say-something era? Was there housekeeping personnel that hadn’t received training? Maybe it was a new person? I don’t know the answers to those questions yet.”

Sheriff Lombardo and his subordinates have kept a relatively low news media profile in the aftermath of the shooting. Police leaders here have declined almost all interview requests, have skipped the cable-news circuit and have emphasized that they would speak with a single voice to ensure that only accurate information was released. Las Vegas officials say that that approach limits distractions and allows investigators to get on with their work. But it is a departure from the way major events have been handled by local authorities in other cities, where live broadcast interviews and news leaks have been more common.

Most of what the media gets from Sheriff Lombardo comes at his frequent news briefings, where his answers may be somber, combative or collegial, depending on the question. His relatively tight-lipped approach has drawn attention to his crisis management style.

“He is very methodical,” said Jonathan Thompson, the executive director of the National Sheriffs’ Association, who called Sheriff Lombardo “a lawman’s lawman.” “He is exhibiting years of training to make certain the chain of custody on the evidence is protected, but more important, the rights and safety of his community are protected, too.”

Longtime colleagues say he is a smart tactician with a down-to-earth manner who does not like to speak in public. His handling of the mass shooting and his tight grip on the release of information have drawn praise from Nevada politicians. But the sheriff has also frustrated some people with his reluctance to divulge details about the case, and he has not hesitated to call out journalists for inquiries that he deems superfluous or repetitive.

“That’s just a different way to ask the same question,” Sheriff Lombardo said disapprovingly on Wednesday night when a reporter pressed him about the gunman’s financial records. “I can’t answer that.”

Even as he has warned against speculation and conjecture concerning the case, Sheriff Lombardo has at times shared his own theories about the actions of the gunman, Stephen Paddock.

“Do you think this was all accomplished on his own?” Sheriff Lombardo said in that same briefing on Wednesday. “Face value, you’ve got to make the assumption that he had to have some help at some point, and we want to ensure that that’s the answer. Maybe he’s a super guy, a superhero — not a hero. Super, I won’t use the word. Maybe he’s a super yahoo that was working out all this on his own. But it would be hard for me to believe that.”

As the elected sheriff of Clark County, Sheriff Lombardo has an unusual role for an urban police leader. Unlike most big-city police commissioners, he manages a combined sheriff’s and police department, and is directly accountable to voters. His agency employs about 3,500 police and corrections officers, and patrols a land area larger than Connecticut, much of it unsettled desert.

Elected by a narrow margin to a four-year term, Sheriff Lombardo, a Republican, is in the early stages of a re-election campaign. His political allies say he is a caring man with a sharp memory and analytical mind, but is not a natural campaigner. Steve Wolfson, the Clark County district attorney, said Sheriff Lombardo “was a little rough around the edges” the first time around.

“I said: ‘Joe, smile more — you’re a good-looking guy. You never smile!’ ” said Mr. Wolfson, adding that he had been a friend of the sheriff for about 20 years.

Gary Schofield, who retired from the Las Vegas police this year as a deputy chief, said, “Joe is not a politician,” but rather “a cop who happens to be in a political job.”

Sheriff Lombardo calls himself a moderate and says that, unlike many in his party’s right wing, he supports some forms of gun control.