KALAMAZOO, MI - Investigators confirmed Thursday that a federal lawsuit filed this week against Uber by a person purporting to be Kalamazoo mass shooting suspect Jason Brian Dalton is bogus.

"He said he has no idea what it is," Kalamazoo County Undersheriff Pali Matyas said of Dalton. "He said he didn't send it, didn't authorize it, doesn't know who did."

The two-page, hand-written complaint was mailed March 11 and filed Tuesday in U.S. District Court for the Eastern District of Michigan in Detroit. It sought $10 million in punitive damages from Uber Technologies, Inc. claiming the company caused Dalton emotional distress and that he had "psychological damage because of Uber."

Police and prosecutors have said Dalton, 45, of Cooper Township, was working as an Uber driver on Feb. 20 when he is accused of going on a shooting rampage in and near Kalamazoo that left six people dead and two others seriously injured.

The lawsuit was mailed in an envelope that listed Dalton's name and the Kalamazoo County Jail as a return address but the postmark on the envelope showed it was mailed to Detroit from Philadelphia, Pa.

"That's what alerted us, the Philadelphia postmark," Matyas said of his agency's decision to look into the authenticity of the lawsuit.

After the purported complaint was received by the court, it was assigned a case number and loaded into the federal court's publicly accessible filing system

In addition to speaking with Dalton, Matyas said investigators also did a comparison between Dalton's handwriting and the handwriting on the lawsuit filing and determined the two are not a match.

Rex Hall Jr. is a reporter for MLive.com. You can reach him at rhall2@mlive.com. Follow him on Twitter.