"DPD is responding to a shooting at East High School. Unknown number of victims at this time. Investigators are working to gather information, expect large police presence in the area," the Denver department announced on Twitter.
Further updates by the department confirmed that at least two adult victims have been located and transported to local hospitals.
One of the victims is considered to be in serious but stable condition, and the other is currently undergoing surgery and is listed in critical condition, the department added.
"It was a student, as was alluded to, as part of a safety plan, undergoing a search. During that search, obviously, a weapon was retrieved, a handgun was retrieved and several shots were fired, striking those two individuals," said Denver Police Chief Ron Thomas during a briefing.
Thomas added that after the incident the student fled the school and their location is unknown. A search is currently underway to locate the individual, whose identity is known.