On Monday morning, news broke that Donald Trump had fired his controversial campaign manager [1], Corey Lewandowski. Lewandowski gained national attention in March after he was charged with battery for grabbing a female reporter's arm at a Trump rally [2].

Here's what you need to know about the drama and why it's not a good sign for the Trump campaign, especially considering his disastrous polling numbers against Hillary Clinton [3].

1. Hardly anyone within Trump's campaign knew it was coming.

Zeke Miller, a political reporter with Time magazine, writes:

Trump campaign source says staff wasn't informed on Lewandowski exit in advance. "No one knows what's going on."

— Zeke Miller (@ZekeJMiller) June 20, 2016 [4]

2. Trump's children encouraged him to fire Lewandowski and gave him an ultimatum.

This is how the firing went down, according to Gabriel Sherman, the national affairs editor at New York Magazine.

Hearing Lewandowski was escorted out by Trump security this morning. His firing was result of coup by Trump children, campaign source said.

— Gabriel Sherman (@gabrielsherman) June 20, 2016 [5]

my first crack at the Corey Lewandowski firing: the Trump kids did it https://t.co/gG9TDjMSvO [6]

— Gabriel Sherman (@gabrielsherman) June 20, 2016 [7]

3. People within Trump's campaign are happy to see Lewandowski gone.

Michael Caputo is a senior adviser within Trump's campaign. Shortly after news of Lewandowski's firing broke, he tweeted, "Ding dong the witch is dead."

Ding dong the witch is dead! https://t.co/pSqQwmAGz1 [8] pic.twitter.com/5dE7GMeEK6 [9]

— Michael Caputo (@MichaelRCaputo) June 20, 2016 [10]

It's been widely reported that Trump strategist Paul Manafort also feuded with Lewandowski [11]; Manafort will replace Lewandowski to head up Trump's campaign, according to Reuters.

This is the latest in a series of ruinous headlines for Trump, including his heavily criticized response to the Orlando, FL, shooting [12] and his racist comments about the Latino judge [13] overseeing the Trump University lawsuits. Here's how Sahil Kapur, a political reporter for Bloomberg, characterized Lewandowski's firing:

Dropping Lewandowski is the clearest sign Trump knows he's sinking. Stood by him through battery charges and turf wars with Manafort.

— Sahil Kapur (@sahilkapur) June 20, 2016 [14]