Paul Ceglia, who was under house arrest awaiting his May 4 trial, is believed to be traveling with his wife, two sons and family dog, according to a bulletin from the U.S. Marshal's Office.
"Everyone has been focused on him, but our greatest concern is where are his wife and children," Ceglia's attorney, Robert Ross Fogg, told ABC News today. "I don't know if the marshals have dusted for prints or have ruled out foul play."
Fogg said it was not yet clear whether a third party may have been involved or if Ceglia cut off his own bracelet and took his wife and children with him.
Ceglia claimed in a federal lawsuit that he gave Zuckerberg $1,000 in start-up money when the Facebook CEO was a student at Harvard University in exchange for a 50 percent share of the future company. That lawsuit was dismissed after a court deemed that Ceglia created fraudulent email evidence.
Prosecutors filed mail fraud and wire fraud charges that carry up to 40 years in prison. Ceglia has pleaded not guilty.
Authorities are unable to pinpoint the moment Ceglia went missing last weekend. After slicing off his electronic monitoring bracelet, authorities said Ceglia attached it to a motor-driven device to make it appear as though he was still wearing it and moving around his home in Wellsville, New York.
When authorities visited Ceglia's home on Sunday, no one answered, according to documents filed in the 2nd U.S. Circuit Court of Appeals in Manhattan. However, they said they were able to hear a mechanical noise inside the home. They came back Sunday night with a search warrant and entered the home, where they found Ceglia's bracelet hanging from a contraption on the ceiling, according to the documents.
The bracelet's charger was also connected to a timer, allowing authorities to still receive the same reports they would get when Ceglia periodically charged his device, according to the documents.
"The facts may suggest a high likelihood he may have [removed his bracelet on his own] but the actual fact that he did something is not there," Fogg said, suggesting there is no definitely proof that his client was the one who cut the bracelet.
Fogg said he has tried emailing Ceglia but has not received a reply.
A missing persons report was filed Wednesday for Ceglia's wife, Iasia Ceglia, and his two sons, Joseffinn, 11, and Leenan, 10, according to the Associated Press.
Iasia Ceglia's sister, Brianna Caster, told ABC News she wasn't surprised Ceglia "would attempt something like this" but said it was unlike her sister to simply leave without telling anyone.
"We don’t believe she would participate in this willingly," Caster said. "Just from what we know in the past, we wouldn't put it past him to say the kids are coming with me with or without you. She puts everyone before herself and would want to make sure her kids are safe."
The Associated Press contributed to this report.