The grandmother also was curious to learn how this had happened.

奶奶也很想知道这是怎么发生的。

youdao

He wanted to know how this had happened.

他想知道这件事是怎么发生的。

youdao

I asked Facebook about this repeatedly, and they refused to directly answer how many times this had happened, if ever.

我再一次问他们这个事件，他们却拒绝直接回答我这种事情发生了多少次。

youdao

How had this disaster happened?

NEWYORKER: After the Movie

"He had problems explaining how this happened, " Sessions told Robert Siegel about the day-long hearing.

NPR: Sen. Sessions: 'Sad Day' for Gonzales and Agency

She said that when she told Millie's mother this, she had asked her how the injuries could have happened.

BBC: Barry McCarney