A smirking JOHN HINCKLEY Jr. is walking around free as a bird – and sources say that has former first lady NANCY REAGAN terrified!

After spending decades in a locked-down mental hospital for trying to assassinate President Ronald Reagan, Hinckley now spends 17 days each month with his mother in her posh home near Williamsburg, Va.

The pudgy 58-year-old has been photographed leisurely strolling through town, and his newfound liberty has apparently put ailing Nancy on edge.

“Nancy doesn’t deserve this,” a friend told The ENQUIRER. “She’s 92 years old and very frail. Her friends are afraid that these photos will put her in her grave.”

Hinckley is ordered to carry a GPS-monitored cell phone, and he’s reportedly watched by the Secret Service while out and about – often eating lunch at local fast food joints and driving a Toyota Camry. But “there’s not much keeping him from giving that phone to a street bum and driv­ing or hopping on an airplane to California,” noted the source. “Nancy has very good reason to be in fear for her life!”

Hinckley opened fire on then- President Ronald Reagan’s entourage on March 30, 1981, in Washington, D.C., seriously wounding Reagan and his press secretary, James Brady.

Hinckley was obsessed with “Taxi Driver” actress Jodie Fos­ter, and the attack on Reagan was a twisted bid to get her at­tention. He was found not guilty by reason of insanity and confined to St. Elizabeths Hos­pital.

After his attorneys claimed he’s in “full re­mission” from his depression and psychotic disorder, a court ruling allowed Hinckley to spend more unsupervised time with his mother, Jo Ann.

“But why would the unsuspecting people of Williamsburg want this would-be murderer wandering around in their midst?” the source wondered. “Who knows when that nutcase could snap again?

“I think he’s not only dangerous to Nancy Reagan and Jodie Foster, he’s dangerous to society. He should be locked up for the rest of his life!”