A grand jury Thursday indicted Bryon Hefner, the husband of Senator Stanley C. Rosenberg, on multiple charges of sexual assault, criminal lewdness, and distributing nude photographs without consent.

The indictments, issued by a statewide grand jury, follow a joint investigation by the attorney general and the Suffolk district attorney into allegations by several men, first reported by the Globe, that Hefner assaulted and harassed them during the past few years, when Rosenberg was Senate president.

The alleged victims told the Globe that Hefner boasted of his influence on Beacon Hill and that they were reluctant to report his assaults for fear of alienating his powerful husband and harming their careers. Two of those men say they are among the four victims cited in Thursday’s indictment.

The indictments are a dramatic turn in a months-long controversy that led Rosenberg to step aside from the presidency late last year.

Hefner, 30, was indicted on five counts of indecent assault and battery. The indictments allege one victim was assaulted on three occasions in Boston in 2015 and 2016 — once in an apartment, once in a restaurant, and once in a car. That alleged victim told the Globe last year that Rosenberg was present in the car but that he did not know whether the then-Senate president was aware of the assault. The Globe found no evidence that Rosenberg, 68, knew of any of Hefner’s alleged assaults. According to the indictment, Hefner sexually assaulted another victim in 2014 and exposed his genitals to that same victim in 2016, and assaulted a third victim in the summer of 2016.

Prosecutors also say Hefner obtained nude and partially nude photographs of another victim without his knowledge, and sent or showed the pictures to four other people without the victim’s consent.

“Today’s indictments send a clear message that we will not tolerate behavior of this kind,’’ Attorney General Maura Healey said in a statement, thanking the victims for coming forward.

District Attorney Daniel F. Conley said the joint investigation had revealed “a disturbing pattern of conduct that was not only inappropriate, but criminal. . . . We know the facts specific to this case, with many of the parties working in politics and government, made it especially daunting to come forward.’’

Hefner will receive a summons to appear in Suffolk Superior Court on April 24 to be arraigned on the charges. Most of the counts carry a maximum sentence of five years in state prison.

“It’s surreal,’’ one of Hefner’s alleged victims said. “I know most survivors of sexual assault never get their day in court. I’m still afraid of what happens next, but I’m also confident that all of the survivors are going to be able to get through it.’’

He also said he hopes Hefner “is somewhere praying.’’

Hefner’s attorney, Tracy Miner, said he would plead not guilty to the charges.

“Mr. Hefner . . . looks forward to contesting the allegations in a court of law, where evidence must be produced and witnesses can be confronted,’’ she said in an e-mail.

In a statement to the Globe in November, Hefner said he was shocked by the men’s allegations and could not respond to anonymous accusers. If the case proceeds to trial, those who accuse him of assaulting or exploiting them will probably face him in a courtroom.

Rosenberg, in a statement, said: “These are serious charges. They are now being handled by the judicial system. I have faith in that system and trust that it will adjudicate this case fairly.’’

The indictment will likely intensify the turmoil that began in the Senate after the allegations first surfaced, costing Rosenberg his Senate presidency and leaving the chamber in disarray as others jockeyed to replace him. It comes just as a senator has claimed the votes to be the next president and legislators are attempting to move forward with the business of lawmaking.

In an emotional statement the day after the allegations against his husband first emerged, Rosenberg said he was heartbroken and expressed sympathy for those who said Hefner had assaulted them. Rosenberg, who had vowed that there would be a firewall between his personal life and State House business after an earlier controversy over Hefner’s meddling in Senate business, insisted again that Hefner had no influence over the business of the Senate.

He said Hefner had entered an inpatient treatment center for alcohol dependence. The couple has since separated.

Acting on claims that Hefner had boasted of his influence on Beacon Hill, Rosenberg’s Senate colleagues launched an independent investigation to determine whether the then-Senate president had violated chamber rules. That investigation is pending. Rosenberg stepped aside as president, initially for the duration of the Senate investigation, and Senator Harriette Chandler temporarily assumed the presidency.

Her tenure was extended after the Globe revealed in February that Hefner appears to have been more involved in Senate business than Rosenberg had claimed, with documents and some who dealt with Hefner revealing that he had access to the Senate president’s official e-mail, calendar, and contacts; had lobbied on a budget amendment; and showed a deep knowledge of Senate matters. Rather than waiting for the investigation to conclude, senators have decided to move on: Last week, Ways and Means Chairwoman Karen Spilka announced she had rounded up enough votes to be their next president.

Current Senate President Chandler called the charges against Hefner “deeply disturbing’’ and applauded the victims for coming forward to authorities.

“Clearly, the actions described will not be tolerated, and the Senate will cooperate fully with the district attorney and attorney general’s office,’’ she said. “These charges illustrate why it is critical that the [Senate] investigation be completed in as thorough a manner as possible.’’

In a statement Thursday, Spilka called the Hefner indictments “the latest turn in one of the toughest periods in the history of the state Senate.’’

“My colleagues and I are heartsick for the victims of these alleged crimes,’’ Spilka said. “There is simply no place for assault and harassment of any kind. While this and other investigations continue, it is important for all potential victims to feel safe to come forward to investigators so that the full truth can be known and addressed.’’

Senator Barbara A. L’Italien, an Andover Democrat who is running for Congress, said Thursday was “a very sad day for the Senate.’’

But, she added, “I do believe that the victims now feel that their stories have been heard, have been taken seriously, which I was advocating for all along. I’m sure they now feel they’re on the path toward justice being served.’’

Senator Bruce E. Tarr, the Senate minority leader, said he hopes the criminal justice system works “swiftly and effectively to address what’s been alleged.’’

“The behavior alleged in these indictments is shocking, it’s despicable, and it’s completely unacceptable,’’ Tarr said.

A spokeswoman for Governor Charlie Baker said he and Lieutenant Governor Karyn Polito “commend those who came forward to report these despicable actions and believe those who engage in crimes and sexual harassment of any kind must be held accountable.’’

One of the men who told his story to the Globe, but who is not among the victims included in the indictment, was distressed to learn yet more men allege Hefner assaulted them.

“There are so many victims,’’ he said. Coming forward last year “was the right thing to do,’’ he added. “I feel some validation in that.’’

The investigation into Hefner will continue, Healey and Conley said, and they appealed to others with information or allegations related to the case to contact them.

Globe columnist Yvonne Abraham can be reached at yvonne.abraham@globe.com. Follow her on Twitter @GlobeAbraham. Joshua Miller of the Globe staff and Globe correspondent Matt Stout contributed to this report.