what is going on with the 43 missing mexican students Massacre

I dont watch tv so I dont watch the news, I logged into an old social media acvout and saw this popping up everywhere. I would like to know the story behind it, I tryed google but I can only get recent update news.

Apparently this was a group of 43 students who went missing in mexico, i believe the mayor along with other officials captured these students and turned them over to a mexican cartel who put all the students into the back of trucks and shot them all, cut off there body parts and burnedthem to ashes.

There is kaos all over mexico with protestors trying to break into the presidential palace and burning down its entrance, demanding justice, accusing the government fir being involved.

I am totaly lost with this story, what were the students doing that they were arrested by mexican police, why would they get turned over to a mexican cartel by the mayor, how was the mexican hov involed.

Can anyone provide a backstory, or a link to it, everything coming up on google doesnt really mention the backstory.