A shooter opened fire Wednesday morning during Mass at a Minneapolis Catholic school , killing two children and injuring 18 other people before dying by suicide, officials said.

The shooting happened at Annunciation Catholic School at the start of the third day of school.

Of the 18 injured, police said 15 were children. Only one person — a child — was in critical condition, authorities said.

The shooting was the latest in a long list of attacks targeting students since the 1999 Columbine High School massacre in Colorado.

Here are some of the things to know about the shooting at Annunciation Catholic School.

What do we know about the victims?

Fletcher Merkel, 8, and Harper Moyski, 10, were killed while sitting in a church that was packed with teachers, parents and schoolchildren

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