YUCAIPA, Calif. — Residents of a Southern California neighborhood are on high alert following the unsettling delivery of mysterious letters, prompting a police investigation to identify the sender.

Security footage from a home in Yucaipa, a city in San Bernardino County, captured a masked individual leaving a letter at the doorstep on Monday night. The person then blew a kiss towards the camera before departing. Similar deliveries were reported at several other homes in the area during the late hours.

Neighbors revealed that the letters, disguised as Christmas cards, contained disturbing messages that were described as vulgar, intimidating, and sometimes even threatening.

“They were inside Christmas cards, but the content was reminiscent of things associated with Antifa,” remarked local resident Scott Ungar.

Ungar noted that each card carried a unique message, with one card specifically including a date accompanied by a foreboding warning.

“One of the cards over there mentioned a particular date, stating ‘You’ve been warned,’ as if to imply that something significant might occur on that day,” he explained.

One street over, another resident, Jaret McComas, found a card addressed not to him, but to Santa.

“Picked it up, opened it, and it said, ‘Dear Santa, I want the head of a Nazi under my tree for Christmas,’” McComas said. “I was like, ‘That is a little weird.’”

McComas said neither he nor his neighbors who received the cards display political signs or affiliations. The randomness of the homes targeted has left residents unsettled.

“I am so confused by that,” McComas said. “I am not a heavy conservative. I’m gay, engaged to my fiancé Roger. So, it’s just kind of concerning for me because I am like, ‘What did I do?’”

He said he wondered whether the American flag outside his home might have drawn attention, but noted that not every targeted house had one, deepening the mystery.

Concerned residents contacted the Yucaipa Police Department. According to neighbors, police reviewed security footage and determined that two masked individuals were involved in delivering the letters.

“When you have people roaming your neighborhood in black face masks, leaving violent notes and warnings, it’s kind of disturbing,” said Ungar.

The San Bernardino County Sheriff’s Department, which makes up the Yucaipa Police Department, said it has increased patrols in the neighborhood.

Residents have also said they will be adding more cameras and security to their homes.