'Time for our country to take a look in the mirror': Parkland student calls for change after massacre

After at least 17 people were killed at his high school on Wednesday, a Marjory Stoneman Douglas High School senior is saying it's time to reflect on the problem of mass shootings.

"This is a time for our country to take a look in the mirror and realize there is a serious issue here," David Hogg said on Good Morning America.

Hogg was at the school when the shooting started and hid in a classroom. He said that the school had done safety training recently, and he believes that saved hundreds of lives.

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Witness: This is something we can't let keep happening. Report from Good Morning America on February 15, 2018.

He said all of his friends are OK, but his younger sister lost two best friends.

"What I wish people would know is that, this is something that we cannot get used to," he said. "This is something that we can't let keep happening. Because if we do, and if we get used to it, it's going to happen again."