The shooting occurred at East High School in the City Park neighbourhood just before 10 am. Authorities know the suspect’s identity and were looking for him, Denver Police Chief Ron Thomas said during a press conference. Police and school officials did not identify the suspect.

“This particular student had a safety plan that was in place where they were to be searched at the beginning of the school day every day,” Thomas said

While the staffers, both of them male, were conducting that search, several shots were fired, the chief said. The handgun used in the shooting was not recovered at the school.

The victims were taken to a hospital where one was in critical condition and undergoing surgery, and the other was in serious but stable condition, Thomas said.

Dozens of shootings at US schools causing death or injuries occurred in 2022. One of the deadliest took place in May when a gunman killed 19 children and two adults in Uvalde, Texas.

Classes were cancelled for the day for East High’s 2,500 students and will not resume this week. When they do, two armed police officers will be posted at the school until the end of the school year, said Alex Marrero, the district’s administrator.