article_snippet.sent: Scroll down for video .
article_snippet.sent: Shockingly, authorities thought that only one person had been killed by the impact, but discovered to authorities
article_snippet.sent: horror that an entire family had been crushed to death according to KIRO TV.
article_snippet.sent: KING-TV added: 'There was nothing anyone could do.
article_snippet.sent: It was just surreal.'
article_snippet.sent: It remains unknown what caused the 'very heavy' concrete structure to fall, KING-TV reported.
highlights_snippet.sent: Police say entire familywould have known nothing about it' as the concrete came down so fast and quick .