Amid concerns of violence targeting college campuses and politicians on Thursday, a threat to the U.S. Naval Academy prompted security officials to lock down the Yard and order midshipmen to shelter in place.

A rumor spread quickly through a popular student messaging app: There was an active shooter roaming the Annapolis campus; the shooter could be disguised as a police officer.

The situation escalated with one midshipman shot and injured in what officials believe to be a case of mistaken identity. There was no active shooter, they say, but the scene Thursday night revealed the anxieties and tensions that have gripped the nation after the assassination of right-wing political activist Charlie Kirk at a college in Utah.

On Friday, authorities announced that they had arrested Tyler Robinson, 22, of Utah, in the killing of Kirk.

In Annapolis, the lockdown was lifted early Friday at the Naval Academy as officials worked to unravel the confusion from the night before.

Navy officials have said little publicly about what happened, other than confirming that one midshipman was injured. He was treated at a hospital and released on Friday, according to statement Friday from the Naval Academy.

U.S. Rep. Sarah Elfreth, who represents Annapolis and serves on the Naval Academy Board of Visitors, said she left Capitol Hill for Annapolis after learning the Naval Academy was locked down.

On Friday morning, she said not much had changed. An investigation into what happened and what lessons can be learned will begin. She reflected on the heightened anxiety on the campus and across the country. The violence and subsequent threats have consumed a generation, she said.

“Every Midshipman at that academy right now has grown up their entire lives in the era of school shootings,” she said.

“Political violence and gun violence is wholly unacceptable,” she added. “We all need to take a breath.”

She urged Marylanders to reflect on what it means to be a community and think about their collective humanity.

Shortly before 5:30 p.m. Thursday, military and local police responded to the Naval Academy after the reports of an active shooter on the campus. Officers began checking rooms of the huge dormitory Bancroft Hall.

While sweeping one room, a Navy officer encountered a midshipmen who hit him in the head with the butt of a parade rifle. Firearms are not allowed in the dorm. Officials believe the midshipman mistook the officer as a threat, according to a law enforcement source with knowledge of the incident. The source was not authorized to speak publicly.

The police officer shot the midshipman around the upper arm and shoulder area, the law enforcement source said. Maryland State Police helicopters flew the officer and the midshipmen to hospitals for treatment.

In a message to the brigade later, Capt. David Forman, deputy commandant of midshipmen, confirmed the account, writing that academy officials believe the midshipman mistook a law enforcement officer as a threat and was injured upon engaging the officer. He wrote that the midshipman was in stable condition and receiving medical attention.

He also told midshipmen that Bancroft staff would accompany law enforcement as they continued to clear the dorm.

The threat was later traced to a laptop belonging to a midshipman who had left the academy and was at his parents’ house in the Midwest, The New York Times reported, citing military officials.

The academy remained closed to the public Friday while the incident is being investigated by the Naval Criminal Investigative Service and other law enforcement, according to the academy’s statement Friday.

Banner reporter Brenda Wintrode contributed to this article.