Large blocks at the end of day of seconds after 4pm are typically market makers (MM's). They trade on behalf of institutions. Unfortunately you don't know if they were buying or selling.
For example A Market maker receives a buy order for 500,000 shares and the buyer isn't going to pay any more than $2.20 The Market Maker could have shares in their account (which are not counted in the float). If not, they have to acquire the shares. The Market Maker wants to make as much money as possible on the trade. So they use every trick in the book to make sure the shares are as cheap as possible. They could short a few thousand shares forcing the the stock price down (and therefore have to acquire even more shares) But by shorting the stock and forcing the price down, they trigger other people sell limits and it's a cascade effect. So later in the afternoon, the Market Maker buys all the shares they need. At the end of the day, they deliver the shares on the original order.
Another example of market on close orders (MOC)
2:30PM is the first show of hands, of those selling on the close. The last time is 3:45. During that period, market makers try and balance the trades. Meaning finding buyers for MOC sales, and finding Sellers, for MOC buyers.
Sometime you will see an imbalance to the MOC and that is when you see the price move in the last 5 minutes 3:55 through 4:05 or so. Again either way, up or down. At 2:35 - 2:45 watch the S&P and see if it spikes or drops suddenly when the overall market MOC is out of balance initially. Then again about 3:50PM
This free web site will show the totals around 4:10pm of orders greater than 50,000 shares. MNLO wasn't on it the list last night. https://marketchameleon.com/Reports/StockOrderImbalanceReport If you have a twitter account, you can search for MOC around 3:55 to get the total market imbalance from people who have access. It has to be $2 Billion or more, to be that valuable.
News 
Market Data 
Discover 
AI
