Reinhard's purported reason?
He thought local police had not taken him seriously when he accused his stepson weeks earlier of theft.
"Because of his phone call to the FBI, significant resources [were] were expended trying to determine whether a credible threat existed to the Olympic Games or any American and Russian citizens," FBI Agent Michael Kent Bantner wrote in the affidavit that led to Reinhard's arrest.
Phone calls to Reinhard's residence Thursday were not returned. It was not immediately clear whether he had retained a lawyer.
According to the affidavit, Reinhard first called an FBI tip line on Jan. 15 to report that he had overheard his stepson, a Russian national, plotting a bomb attack over Skype.
He told the agents that he heard his stepson, who was not named in court filings, speak in Russian, but that he clearly understood him say he planned to "attack American assets overseas, especially embassies."
"He's going to [mess] up these Olympic Games and all American interests in Russia," Reinhard is quoted in court filings as telling the FBI tip-line operator. "He's going to kill somebody or a lot of people, and somehow I got to report it."
With tension high over the potential for a terrorist attack on the Olympics - opening ceremonies are Friday - his story quickly made its way up the FBI chain of command.
Counterterrorism officials in Washington contacted the Russian Federal Security Service, which opened its own investigation. Meanwhile, agents from New York; Newark, N.J.; and Philadelphia fanned out in an effort to locate Reinhard's stepson and question his friends and associates.
The more Reinhard talked, the more dangerous the threat he described became.
Before long, he was reporting hearing his stepson say "Chechnya" several times in the conversation, a reference to the North Caucasus territory that has become a hot spot for separatist fighting. He said he saw bomb-making websites on his stepson's computer screen, FBI agents said.
Reinhard had also told Abington police that his stepson had left threatening phone messages warning, "Call the police, and I'll kill you and them," according to Montgomery County Court filings.
But parts of Reinhard's story raised suspicions from the start.
For instance, he allegedly told the FBI tip-line operator that he was a former law enforcement officer.
Questioned about that claim, Reinhard purportedly explained that he had been a deputy mayor of New York City.
Pressed further, Reinhard produced a laminated ID card, the affidavit said, that proclaimed him a commissioner for the New York Taxi and Limousine Commission.
(New York officials could not confirm Reinhard's service on the panel Thursday.)
Then there was the reaction Reinhard's wife, Tatiana, inspired when she walked in to find her husband encircled by FBI agents at their kitchen table on Jan. 16.
He told her he had never contacted the FBI and denied mentioning anything about bombs or terrorism, authorities said.
By the time agents tracked down Reinhard's stepson a day later - as he arrived at a New York airport to board a flight to Russia - the story had become clear.
According to the affidavit, the man cooperated with the agents. They searched his luggage and found nothing suspicious. He told them his stepfather had accused him in early January of stealing a safe from the home they shared - an allegation he denied.
The stepson maintained that he had never had any Skype conversation that could have been perceived as about terrorist bombings, and was merely traveling to his home country to visit a sick grandfather.
Confronted with the inconsistencies, Reinhard said he might have "had a few drinks" before calling the FBI and "exaggerated" some of the claims, the affidavit stated.
According to the document, he told agents he hoped implicating his son in a terrorist plot might achieve quicker results in the theft investigation.
As of late Thursday, Reinhard remained in federal custody, charged with making a false report to the FBI.