Three days earlier, his wife had filed for divorce; he was due to appear in court with her for a domestic violence hearing in about half an hour.
Then, the nicely dressed, gray-haired man peeled open his jacket to reveal what looked like dynamite strapped to his chest, authorities said, and things got much worse.
Police say Eisenberg went to the office Friday demanding to talk to Clinton about helping him get mental health care and ended up taking at least five people, including an infant, hostage. Night would fall before the last one walked free and the hostage-taker peacefully surrendered.
In the meantime, downtown shops, restaurants and homes were evacuated, and nearby schools were placed on lockdown until students could be rushed away on buses.
Authorities said a state police negotiator spoke to the hostages, and then to Eisenberg, eventually persuading him to give up. Shortly after 6 p.m., the suspect walked out of the storefront office, put down a package and was immediately surrounded by SWAT team officers with guns drawn. They put him on the ground and handcuffed him.
The package was not dynamite, but rather road flares duct-taped to Eisenburg's body that were made to look even more realistic by a separate detonator, said Col. Frederick Booth, commander of the New Hampshire State Police.
Clinton, in the Washington area during the day, traveled to New Hampshire Friday night to meet with the hostages, their families and police.
The confrontation brought her campaign to a standstill just five weeks before the New Hampshire primary, one of the first tests of the presidential campaign season. She canceled all appearances Friday, as did her husband, former President Bill Clinton, but she planned to campaign as scheduled in Iowa on Saturday.
"He was someone that was not known to my campaign headquarters until he walked in the door today," Clinton said at a late-night news conference in Portsmouth. "It appears that he is someone who is in need of help and sought attention in absolutely the wrong way."
Rochester police Chief David DuBois said Eisenberg was being held on state charges of kidnapping and reckless conduct, and that federal charges were being considered.
Eisenberg had a hostage call CNN three times and spoke to network staffers during the standoff, CNN reported after the ordeal was over and all the hostages were safe. Eisenberg said he wanted help getting psychiatric care, but had been turned away because he didn't have the money.
"I need to speak to Hillary Clinton," CNN quoted him as saying. "Something's got to change. Ordinary people need help" with their insurance.
The network described Eisenberg as "well-spoken, articulate and impassioned about his cause," but said he became increasingly agitated and laced his third phone call with profanities.
About two hours after Eisenberg let a woman with a baby go, at least one other woman escaped from the office; two other hostages made it out later, the last about half an hour before Eisenberg surrendered, police said.
Soon afterward, police maneuvered a robot to the road flares and triggered an explosion to destroy them.
Eisenberg had been scheduled to appear in Strafford County court with his wife for a domestic violence hearing, according to Foster's Daily Democrat in Dover.
Divorce papers filed Tuesday indicated he had been arrested and charged with criminal mischief, domestic related, and violating a protective order, the newspaper reported. In the papers, Eisenberg's wife said he abused drugs and alcohol and subjected her to severe verbal abuse and threats.
A man who said he was Mrs. Eisenberg's son declined comment Friday night.
Eisenberg also was arrested at least twice earlier this year, once for allegedly driving under the influence and once on two counts of stalking. The status of those cases was not immediately clear.
Diane Wiffin, a spokeswoman for the Massachusetts Department of Correction, said a Leeland E. Eisenberg with the same 1961 birth date as the suspect was released from the state prison in Concord, Mass., in March 2005 when he completed his sentence. She would not give details about the nature of his offense or length of his sentence.
Eisenberg made local headlines in March when he held a news conference on the steps of Rochester City Hall to complain about a police policy of placing fliers in unlocked cars warning motorists to lock their doors.
"This is nothing more than a gimmick to get around the Constitution and go around in the middle of the night upon unsuspecting citizens in their own yard and search their vehicles," he said at the time.
Police, who said they were just trying to reduce theft from motor vehicles, changed the policy in response.