UPDATE: The school lockdown was lifted at approximately 12:00 p.m. CDT, and students were told to resume normal activities, the Associated Press reports. School officials confirmed that the suspect had been arrested and taken into custody by police.

Carroll University in Waukesha, Wis., has been placed on lockdown due to reports of a gunman spotted on campus.

According to Milwaukee news station Today’s TMJ, police placed the university, which has a student population of about 3,500, on lockdown after two students reportedly spotted a man on campus carrying what they described as a “long gun.” Claire Beglinger, a spokeswoman for the university, told local television station WITI-TV that the students alerted public safety officers they had seen the man near the school’s outdoor tennis courts. He was described as white, between 50 and 60 and wearing a brown jacket and black hat.

At 10:39 a.m., the university sent a text alert to students, saying, "Text from Carroll:: Not a test There is a report of a male with a firearm walking near the tennis courts and the Barstow Building on Barstow. remain indoors until further notice [sic]."

The school sent a follow-up text 30 minutes later with a description of the gunman. At approximately 11:25 a.m., police had barricaded Maple Street, nearby the campus, and were reportedly standing by with their weapons drawn.

Corey Garswick, a 20-year-old sophomore at the university, said that tensions were high after Monday's deadly explosions at the Boston Marathon. "Especially after the Boston Marathon bombing, it came as quite a shock," Garswick told the Journal Sentinel.

Some students at the school tweeted about the situation from inside school buildings. “I am currently on a lock down at Carroll University because there is a gunman on campus. #Scared” @BlondeWiscoBabe tweeted, adding, “Ugh I just want to go home.”

Jessie Garcia, a teacher at the school, said as of 11:59 a.m. that all of the buildings were being locked and that her own students were trying to stay calm.

Several other schools in the vicinity, including Waukesha Central Middle School, Saratoga STEM Academy and Randall Elementary, were also placed on lockdown as a precaution.