The handwritten complaint was filed in a federal court in Michigan on Tuesday and entered in its public database the following day.
It accuses Uber of causing Dalton “psychological damage.”
CNNMoney reported on the filing on Wednesday. In response, Uber said it was “hard to know how to respond to someone who refuses to take responsibility for his own actions.”
Matyas told CNNMoney on Thursday that he’s “1,000% sure” that the complaint was a hoax and didn’t come from Dalton.
Matyas said he first became suspicious about the lawsuit on Wednesday evening after noticing that it had a Philadelphia postmark.
“Our Michigan mail doesn’t go to Philadelphia first,” he said, adding that postal markings on the envelope were different than the ones used by the Kalamazoo jail. He said Dalton is able to write letters from jail, but all such mail that leaves the jail is logged.
Matyas said that on Thursday morning, his office did a handwriting verification test based on samples of Dalton’s writing that it has on file. The handwriting didn’t match up. He said his office notified the FBI.
“We went and talked to [Dalton],” said Matyas. “He said, ‘I didn’t authorize anyone to file a lawsuit — and I don’t know who sent this.'”
The complaint was filed with the U.S. District Court for Eastern Michigan and is available on PACER, an online case locator for electronic court records.
The handwritten document claimed that Dalton had been working for Uber for “years,” and that he wasn’t invited to corporate parties or given a Christmas bonus. Uber chief security officer Joe Sullivan said Dalton began working for the company in late January 2016.
Dalton has, however, expressed his grievances against Uber in the past.
Shortly after the shootings, he told investigators he was reluctant to talk because he didn’t want to come across as a “crazy person,” according to documents released Monday and published by CNN affiliate WDIV-TV in Detroit. He went on to tell investigators the Uber app made him “like a puppet” and that it would “take over your whole body.”
Police have said that Dalton does not have a history of mental health issues. Earlier this month, a prosecutor said Dalton would undergo a psychiatric evaluation to determine his competence to stand trial.
Jeff Getting, Kalamazoo County prosecutor, said his office doesn’t believe the suit was filed by Dalton. He said a “competency evaluation” of Dalton “is moving forward.”
The local FBI office and Uber did not immediately respond to requests for comment Thursday.