"It took (the deaths of) two white men to wake up white America what black America in the South particularly knew — that you could get murdered for YOUR OPINION or wanting to vote," said David Goodman, the brother of one of the victims in the incident.

Today if a person is too outspoken on certain issues, he'd probably be watched and monitored by the authorities. In that sense, the Civil Rights Movement has not completely accomplished what it's set out to do half a century ago, not to mention incidents involving blacks getting killed by police, and all cases and forms of discrimination non-whites in US have experienced since the 60s.

2
The film Mississippi Burning is based on this incident.

The incident is also mentioned in the classic rock "American Pie":
Bye bye Miss American Pie
Drove my Chevy to the levee
But the levee was dry...
https://www.youtube.com/watch?v=gpvXPz9u4Zc
The "levee" is referred to the place where the 3 young men were murdered by police.