The gunman in the Connecticut school massacre that left 20 small children dead blasted his way through a locked glass door, climbed through and proceeded with his killing spree, the state governor said.

“He shot his way into the school. The school was locked. He used a weapon to open up the glass, and then walked in,” Governor Dan Malloy said on the ABC program “This Week.”  The shooter, Adam Lanza, fired “a number of rounds,” Malloy said.

Police had previously said Lanza forced his way into the school but it was not clear he did it by shooting his way in.

“He discharged to make an opening and then went through it, went to the first classroom, as you know, went to the second classroom,” the governor said.

He added that authorities believe that, while shooting in the second classroom, the gunman heard police and emergency crews rushing to the scene of the massacre, Sandy Hook Elementary School, and took his own life.

The overall death toll was 28: the 20 children aged 6 or 7, six adults at the school, Lanza himself and his mother Nancy, whom he shot at her home before heading to the school.

Malloy said the first call for help from the school came from someone who was wounded but survived, and that first responders were swift.

“But, you know, this — this sick fellow, you know, clearly mentally ill, killed his mother, proceeded to go on and kill a great number of people,” Malloy said.

The children who survived Friday’s shooting at Sandy Hook Elementary School will not have to return to the scene of the massacre and will attend classes in a neighboring Connecticut town when school reopens.