A threat against Palo Alto High School that led to a lockdown at the school and the nearby district office Thursday afternoon was a hoax, according to police.

Police are looking for whoever called in the threat, which investigators have determined was made from a cellphone that went missing or was stolen earlier in the day at Town & Country Village shopping center.

The police dispatch center took two 911 calls at 12:31 from a cellphone from a male who identified himself by first and last name, according to police.

The caller, whose name police did not release, claimed he was going to "shoot up" the school in 15 minutes, police stated in a press release.

The high school at 50 Embarcadero Road and neighboring district office at 25 Churchill Ave. were placed on lockdown as a precaution, police said. Students were told via the school's public-address system to go into a classroom immediately.

As police investigated the calls, they found that the name provided by the caller matched that of a current student at the school, according to police. When officers tracked down the student in a classroom under lockdown, they learned he was not involved in the incident and his cellphone number didn't match the one used by the caller who made the threat. Officers also searched his property and found no contraband.

Investigators later determined that an adult with no ties to the school owned the cellphone from which the threatening calls had been made. The cellphone owner no longer had the device, which had either been lost or stolen earlier in the day at Town and Country Village shopping center, which is across the street from Paly, police said.

The owner of the cellphone from which the threat had been called in contacted their carrier to deactivate the device once they realized it went missing, police said. As a result, whoever had the phone was able to call 911 from the device, but incoming calls from officers looking to speak with the caller didn't go through.

After police moved throughout the campus with students, teachers and staff under lockdown, they found no violence or anyone physically injured.

The lockdown ended around 2:15 p.m., when people were allowed to leave the campus but not allowed to enter, according to Ken Duecker, director of the city's Office of Emergency Services.

The school released students at the regular dismissal time of 3:25 p.m., interim Superintendent Karen Hendricks said.

Palo Alto officers planned to remain on the campus for the rest of the day, police said.

Detectives are following up on numerous leads from the school community. Police said they are working in close conjunction with school personnel as they continue to investigate.

Paly student Lia Salvaterria told the Weekly via text message during the lockdown that she heard a message over the school's PA system directing people "first to go to a classroom. Then they said it was lockdown."

During the lockdown, police officers and patrol cars were seen blocking entrances to the high school and district office.

Menlo Park and Mountain View police officers in addition to Santa Clara County sheriff's deputies working for the Stanford Department of Public Safety were also at the scene.

Dozens of parents gathered at Town & Country Village in front of the Trader Joe's after their children texted them about the lockdown. Many parents exchanged text messages with their children on the campus and some parents were near tears. A SWAT officer with a AR-15 rifle was seen standing in front of Trader Joe's.

"I can't believe this is happening," one worried mother said.

Parent Jamie Pearson, whose child is a sophomore at Paly, learned about the threat through a friend and was waiting outside the shopping center.

"We're living in different times now," she said. "I just feel sick and powerless."

Theresa Packard, whose daughter is a freshman at the school, found out about the threat through the police department's Nixle account.

"It's good to see such a quick response, but we just need the kids to be safe right now. You hear a lot of things, but you don't know how many people are in there and that's the scary part," Packard said.

Packard's daughter told her mother via text message that she had been in a dark classroom for more than an hour.

History teacher Steve Foug, who was also across the street from campus, said the school received a call that a lockdown was in place at 12:45 p.m. School protocol requires staff to immediately lock rooms and alert anyone off campus to stay away from the school.

Foug said the school has been preparing for such events for a decade and has been refining the protocol to make it as straightforward as possible.

Some Paly students were at Town & Country Village shopping center when the lockdown was ordered. A staff member from Palo Alto High School directed off-campus students to stay away and kept people away from the section of the shopping center parking lot directly across from Paly.

All Paly athletics events were canceled for the day, the school's Athletics Department said on Twitter.

Seniors Nicholas Lee and Cullen Tellez were returning to campus after lunch when they noticed two police cars at the school's back parking lot. The two were halfway into the campus when they realized the campus was closed down. A teacher told them there were threats of a shooter, and they decided to go away from the incident. They waited at Town & Country, they said.

"School is supposed to be a safe space," Lee said. "It's just ridiculous."

"You always see this on the news. We didn't think it could happen here, but yes, there is the possibility of it happening. It just really blows my mind," Tellez said.

"This really should stop," he added. "Enough is enough."

Paly junior Ashley Wang was in journalism class when the class received a message over the public-address system that the school was on lockdown and that it wasn't a drill. She said she felt a bit safer in the school's Media Arts Center than on the central part of campus. Her teacher kept the class calm by offering food, snacks and water. But students were panicky, she said.

"We were all texting our parents and other classmates to see if they were all OK," she said.

School officials made announcements over the address system with updates.

"It felt as if there was a shooter on campus, but there was a lot of confusion and a lot of panic," she said, adding that she still wasn't sure about what had happened.

In general, people on campus were scared, students said. Chesnie Cheung said her classroom barricaded the door with desks. Students were hugging their friends and texting others. Some were reportedly in other classes, Cheung said.

Senior Jackson Clough said at first he wasn't worried when the announcement came over the public address system. He thought it was a drill. But soon students were barricading the doors and pulling down the blinds. He said he felt safer because a teacher was there.

"It was pretty nerve-wracking," he said.

Texting was a good way for students to communicate because not much information had filtered through from the school about what was actually going on, Clough said.

"I just hope it doesn't become as common as fire alarms," he said, noting that about once a month someone sets off the alarm system as a way to get out of class. "I don't want this to happen more than once."

Lee and Tellez said they don't think armed teachers, a proposal President Donald Trump has supported, would help improve campus safety in the event of a shooting. There should be tighter background checks for gun purchases, they said.

Connections between students, teachers and staff are also important to help prevent any kind of violence or crisis, they said.

"We need more caring adults to just reach out," Lee said.

Wang said the incident is sure to spark needed discussion.

"It will move some to open conversations about gun control," she said.

Paly has procedures in place for drills and lockdowns, but there should be more discussion about how to prevent the need for these safeguards in the first place, she said.

Asked how he'll sleep Thursday night, Lee said, "I'll say a prayer, honestly. I'll thank God that everyone is safe, and that's all that really matters.

"I hope this ends soon. No one wants to see another shooting," he said.

Hendricks told the Weekly that that she intends to debrief with her staff and the police about the incident.

"Any time you (have) any kind of a crisis situation ... you want to go back and take a look at the incident and debrief what worked and what the learnings were," she said late Thursday afternoon.

In a message to the district community, she asked families to

make sure their contact and household information is accurate as part of an annual data update that started this week to ensure they will receive information during an emergency.

"The kids were safe, staff was safe and we appreciated the presence of the police department very much," Hendricks said.

Police stated that whoever is responsible for the hoax will face multiple criminal charges, as well as face civil liability to pay for the cost of the sizeable law-enforcement response.

"Hoax threats such as this are not only criminal in nature but they also create a great deal of stress and anxiety for students, parents, school staff and the community," police stated. The incident "took officers away from their other important duties and calls. Anyone found responsible for placing a hoax call like this will be prosecuted to the fullest extent of the law."

Earlier this week, students at Cupertino High School were evacuated after the school received a "robotic call" threatening harm, according to a tweet from the Santa Clara County Sheriff's Office. Students returned to campus after sheriff's deputies determined there was no indication of danger to the school or the neighborhood.

Anyone with information about Thursday's incident is asked to call the department's 24-hour dispatch center at 650-329-2413. Anonymous tips can be emailed to [email protected] or sent by text message or voice mail to 650-383-8984. Tips can also be submitted anonymously through the police's free mobile app, downloadable at bit.ly/PAPD-AppStore or bit.ly/PAPD-GooglePlay.