Orientation activities were placed on hold and some incoming LSU freshmen found themselves barricaded inside classrooms Tuesday while authorities spent hours investigating reports of an armed intruder on LSU's campus before ultimately issuing the all clear.

Alarm spread among some students and faculty during a time of heightened anxiety about gun violence nationally following the mass shootings in Texas and Ohio earlier this month.

But LSU police ultimately determined there was no threat and officials said the initial call probably stemmed from an off-duty law enforcement officer who was on campus for a programming event in Coates Hall, the building that was evacuated while police did a full sweep of all rooms.

Many LSU students arrived on campus last week and over the weekend for orientation and other activities before classes start next Monday. They received a text alert from the university Tuesday afternoon telling them to "Run, Hide or Fight. … Reported armed intruder in Coates Hall." Everyone in the quad area was asked to shelter in place for almost two hours while police searched the building.

The initial report came in about 2:30 p.m. No shots were fired and no one was injured in the incident.

LSU spokesman Ernie Ballard III said officials followed national standards for possible armed intruders or active shooters — including the "run, hide or fight" language that was distributed in the initial alert. LSU officials went so far as to define those three terms in an additional text alert sent to students and faculty, providing them with a link to the federal government's guidelines for people dealing with an active shooter situation.

Ballard said some people questioned whether such language was necessary, but he said officials acted out of an abundance of caution and followed normal protocols. He said it's better to be safe than sorry in a situation like this.

Firearms are not allowed on LSU's campus, unless carried by someone in an official capacity. Ballard said investigators had talked with the off-duty law enforcement agent, who approached officers as they arrived on scene and told them he also believed he was likely the source of the call.

The incident at LSU came just a few weeks after a similar false alarm at a Baton Rouge Walmart when one customer pulled a gun on another, prompting panic inside the store and multiple reports of an active shooter; those reports were later declared unfounded. Authorities in that case attributed the reaction to an American public on edge.

Samantha Fernandez, 18, just moved to Baton Rouge last week from her home country of Honduras, having received a student visa — ready to start her freshman year in LSU's engineering school. She has visited the United States before but never lived here until now.

She said the threat of American gun violence has been on her mind, especially after the recent mass shootings and ramped-up national rhetoric from people on both sides of the gun control debate.

"It was a fear I had when I came here," she said. "Now it's something that will always be in the back of my head."

Fernandez spent hours on lockdown inside LSU's Union Theatre building Tuesday, along with her mom and grandma who were helping get her settled into her new home. They had been planning a trip to the mall to buy more items for her dorm room when they were placed on lockdown. Fernandez said she had just signed up for her first semester classes earlier that day.

About an hour after the initial lockdown, LSU instructor Edward Gibbons III told reporters that he was in Coates Hall late Tuesday afternoon when a teaching assistant told him someone on the cleaning staff had seen a person with a pistol. He said they immediately locked the doors and stayed put, waiting for updates.

Meredith Owens, 18, was also inside Coates Hall with two of her friends from high school attending an information session about how to volunteer at LSU's food pantry, when a police officer poked his head inside the classroom and asked them to stand along the wall without moving. She said it seemed like a drill.

Then another officer with a long gun came in and told them to evacuate. Later the students were relocated to an adjacent building, where they barricaded themselves inside another classroom for hours.

Owens and her friends, who are from Atlanta, said overall they were alarmed but not panicked during the experience, in part because they've lived through threats at their high school and have grown up in the age of active shooter drills.

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Other students seemed wholly unfazed by the threat of an armed intruder on campus, as a group of people started up a kickball game on LSU's parade ground, several yards from the crime scene tape, during the law enforcement investigation.

LSU officials announced around 5 p.m. that the search was over and campus operations could return to normal.

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#LSUPD just put red crime scene tape around the perimeter of Coates Hall @theadvocatebr pic.twitter.com/f1C95cHhAX — Hilary Scheinuk (@hscheinukphoto) August 20, 2019

Very heavy law enforcement presence around Coates Hall at #LSU. Several #LSUPD and @BRPD officers on scene with long guns. They’ve pushed us back to the Union @theadvocatebr pic.twitter.com/LRDi6Ndd1t — Hilary Scheinuk (@hscheinukphoto) August 20, 2019