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On Wednesday morning, more than 20 squad cars arrived at Mar Vista High School in Imperial Beach looking for a student who police said called the Sweetwater Union High School District and claimed he killed his father and was going to kill himself on campus. The call prompted school officials to lock the school down shortly after 9 a.m.

Nearby Imperial Beach Elementary School was also locked down by school officials, and many parents rushed to the schools to pick up their children after receiving calls from the students that they were on lockdown.

10News learned the school district then received three more phone calls from people saying they were going to kill themselves on the Mar Vista campus.

Authorities searched the area but did not find any gunmen, and the lockdowns were lifted about an hour later. Investigators have ruled the calls a hoax. On Tuesday, threats of a rooftop shooter and explosives planted on the Mar Vista campus were also untrue.

"The school is safe," said Mar Vista High School Principal Wes Braddock. "There is no evidence that the safety of this school has been compromised over the last two days."

The San Diego County Sheriff's Department said they believe one man is behind the threats made to Mar Vista High on Tuesday and Wednesday. Sheriff's officials said a woman is also involved and there could be more people. They do not believe students are involved.

Sheriff's officials said it is possible the individuals are linked to the website PrankU.net, a site for people involved in "swatting."

"It's their idea of funny and it's just not everyone's idea of funny," said Mar Vista High School junior Allison Gray.

Swatting, or SWATing, is a form of a prank phone call that has become a popular topic online. The goal of swatting is to trick an emergency service, such as 911, into dispatching a large response.

"These suspects will post their stories in kind of a bragging rights thing," said sheriff's Lt. Greg Hampton.

Often, the bogus calls are made via computer from miles away or even from other states.

"We recently had one here in our command. It was found that a juvenile had done this," said Hampton.

That teen is facing charges in connection with the prank in Lemon Grove.

Sheriff's officials said the prankster in the Mar Vista High case used out-of-date school information, but is using a proxy server to disguise their location. Sheriff's Lt. Marco Garmo told 10News that indicates the people involved could be former students or someone anywhere in the world using old Internet information to pull a costly prank.

Anyone caught making false police reports could face charges and ordered to re-pay law enforcement for the cost of resources. If someone underage is making the reports, their parents could be asked to take on the financial obligation.