The United States Naval Academy in Annapolis was placed on lockdown Thursday evening after social-media threats from an expelled student and an ensuing accidental shooting near Bancroft Hall, officials and multiple news outlets reported.

Students, staff and faculty received an emergency shelter-in-place alert at 5:32 p.m. advising them to "get inside and lock your door right now. Not a drill," according to a copy of the message circulated during the incident. Local law enforcement and Naval Support Activity Annapolis said they were responding to reports of threats and conducted a search of the base as a precaution.

Initial reports suggested an armed former Naval Academy student had come onto the Maryland campus and was opening fire near the campus’s largest dormitory, but officials later said the threats had been posted on social media and that the person who issued them used an internet address that made it appear he was on campus. Authorities described the situation as evolving and emphasized they were treating the threats seriously while conducting searches.

Amid the chaos, NBC News reported that a student sheltering in place mistook a law enforcement officer for a threat and fired a training weapon at the officer, prompting the officer to return fire. The Daily Mail quoted officials on the scene saying the shooting was accidental. One person was hospitalized and several others were evaluated, and the hospitalized student was expected to recover, according to those reports.

Bancroft Hall, which houses more than 1,600 midshipmen, is among the largest single dormitory buildings in higher education. The proximity of large numbers of students contributed to swift campus alerts and a broad law enforcement response that included local police. Naval Support Activity Annapolis said it was coordinating with local law enforcement agencies and would provide updates as they became available.

The lockdown at the Naval Academy came amid a wave of campus threats and security incidents reported across the country. In Boston, police initially responded to reports of gunfire near the University of Massachusetts Boston that led to evacuations and a heavy police presence before authorities later declared the campus situation all clear. Multiple historically Black colleges and universities reported threats, with Alabama State University temporarily suspending operations and other institutions including Hampton University, Virginia State University, Southern University and A&M College in Baton Rouge, and Florida's Bethune-Cookman University taking precautions or canceling activities.

Stockton University in New Jersey also issued a shelter-in-place order as police investigated an off-campus shooting on Thursday afternoon. The incidents followed the fatal shooting Wednesday of conservative activist Charlie Kirk at Utah Valley University, an event that federal and local law enforcement said has prompted heightened concern and additional investigations. The FBI released an image Thursday of a person of interest in the Kirk case and asked the public for help identifying the individual.

Officials stressed that investigations into the disparate incidents remained active and that details were subject to change as agencies reviewed digital evidence, surveillance footage and witness accounts. The Naval Academy and local law enforcement asked anyone with information about the social-media threats or the night's events to come forward to assist ongoing inquiries.

This is a developing story; authorities and the Naval Academy said they would provide further updates as more information becomes available.