Creepy clowns are coming to Southern California.

So say social media accounts warning of clowns showing up and promising harm at schools. Police departments were flooded Wednesday with calls of threatening clown behavior and are watching for any problems.

A rash of public complaints and social media reports of people dressed as clowns and acting suspiciously has swept several states the past few weeks. Sightings have occurred across California, including Modesto.

The reports show scary-looking people skulking near the woods, schools or highways, usually at night.

Even horror author Stephen King, whose book “It” featured a killer-clown named Pennywise, chimed in. He took to Twitter this week to urge an end to the clown phenomenon.

“Hey, guys, time to cool the clown hysteria …” he wrote.

The Los Angeles County Sheriff’s Department on Wednesday said that it is getting reports of males in Lancaster wearing clown masks and possibly threatening pedestrians with kitchen knives.

The Instagram account, WeAreComingToCali, popped up Tuesday with the ominous warning “We are coming to LA tomorrow! We will be invading Los Angeles, Carson, Culver City, Torrance, Crenshaw, Inglewood, Pasadena, Compton, Lakewood, Palmdale etc. !!” and 11 posts of frightening clowns hanging out in various locations.

The Pasadena Police Department said it is aware of the Instagram account and the reference to Pasadena.

So far, there have been no reports, sightings or threats from creepy clowns in Pasadena, Pasadena Lt. Pete Hettema said. No other police agencies in the San Gabriel Valley reported any sightings.

In the San Gabriel Valley, Glendora police arrested a 19-year-old apparent creepy clown enthusiast and former student of Sierra High School on Wednesday on suspicion of making threats against his alma mater, as well as toward the city of El Monte, authorities said.

William Salazar is accused of making criminal threats via killer clown-dedicated Instagram and Facebook accounts, Glendora Police Chief Tim Staab said.

Students at Sierra High School began receiving posts from the account Tuesday night which threatened violence, Staab said. Students notified parents and school administrators, who contacted police Wednesday morning.

“Sierra skool gonna get hit (tomorrow) say your blessing #(expletive)skooliwasaclassclown,” read on of the posts.

“Bout to kill (expletive) in el monte whoever outside better know how to throw dem hands or shoot #ittimetoshowweanitclowingaround,” read another grammar- and spelling-shirking post.

The Instagram account had been taken down Wednesday afternoon, however the Facebook page remained online. The Facebook page, which was started on Monday, features pictures and videos of menacing-looking, sometimes ax-wielding clowns.

Investigators soon determined the identity of the alleged poster.

“We tracked him to a relative’s house in Kern County,” Staab said.

Salazar was expected to be booked on suspicion of making criminal threats and held in lieu of $50,000 bail pending his initial court appearance.

The suspect indicated to detectives that he authored the posts as a joke, but Staab said he found no humor in it.

“These types of threats are taken seriously by law enforcement, and if you make a threat against somebody, there’s a good chance you’re going to get arrested,” the chief said.

In Riverside County, one posting threatened that clowns would kidnap or kill teachers later this week.

The Temecula Valley Unified School District posted on its Facebook page a social media threat warning, “We will be at all High schools this friday to either kidnapp [sic] students or kill teachers going to they cars …” accompanied by the hash tag, #WeNotClowninAround. The original post from user “Aint Clownin Around” has been removed.

School officials called the unconfirmed clown sightings a “disturbing trend” and “a form of cyber terrorism and swatting intended to create panic in the schools.” Swatting involves calling and coaxing police dispatchers into sending officers to a location based on a false report of a crime.

Schools say the reports of clown sightings are no laughing matter.

Elliott Duchon, superintendent of the Jurupa Unified School District, said he’s taking the situation seriously, though officials haven’t had any reports of scary of suspicious encounters with clowns.

The district is telling principals to have “heightened awareness” of people dressed as clowns and behaving in a threatening way, Duchon said.

As Halloween approaches, some kids will wear clown costumes, and Duchon said he doesn’t want to dampen their enjoyment.

“Principals are going to have to watch for anything that’s beyond fun and games,” Duchon said. “If they’re in a clown suit and acting inappropriately, they’re going to be disciplined.”

Temecula school officials are telling parents to remind their kids not to contact strangers as well as the risks and consequences of social media posts. The district urged any suspicious activity to be reported immediately.

In San Bernardino County, Fontana police reported Wednesday that they have received “calls and social media inquiries claiming subjects dressed as clowns are making threats towards citizens,” a statement said.

Police are monitoring the situation and working with Fontana Unified School District police to ensure students’ safety.

A Twitter account that purported to list “clown sightings” flagged multiple locations in the Temecula Valley on Monday.

About 11 a.m., the @ReportClowns account, which has since been deleted, posted sightings at Murrieta Mesa High School, Rancho Vista High School in Temecula and the Promenade mall in Temecula.

There was no information on the account as to the nature of their attire or their activities.

Authorities — including officials with the Temecula Valley Unified School District, Police Department and Promenade mall security — had no reports of clown appearances, which could mean the alleged sightings were a prank.

“Per my Security staff, there were no CLOWN sightings on property today,” Kym Espinosa, director of marketing for the mall, wrote in an email.

Many reported clown sightings are hoaxes.

For example, four young children told police they made up stories about spotting clowns in unusual places in and around Annapolis, Md. A 24-year-old man from Winston-Salem, N.C., was charged with falsely reporting that a clown knocked on his window.

Other related cases weren’t so harmless and resulted in criminal charges.

The sheriff in Escambia County, Ala., recently arrested a 22-year-old woman and two juveniles after Flomaton High School was locked down and searched when students were threatened on “Flomo Klown” and “Shoota Cllown” social media accounts.

And in Athens, Ga., an 11-year-old girl was arrested on suspicion of taking a knife to school Friday because she was frightened by social media reports and other rumors that clowns were preparing to attack children.

Staff writers Aaron Claverie, Beatriz Valenzuela, Daniel Tedford and The Associated Press contributed to this report.