Shares were trading at $49.54 as of 8 p.m., down 3.77% from the closing price of $51.48 Friday afternoon. Twitter the ban at 6:21 p.m.
Trump's account was temporarily suspended on Wednesday after a mob of his supporters stormed the U.S.Capitol.
When the president's account was reactivated Thursday, he sent out two tweets, saying that his supporters "will have a GIANT VOICE long into the future" and that he will not attend President-elect Joe Biden's inauguration.
After Trump sent those messages, Twitter said it "determined that these Tweets are in violation of the Glorification of Violence Policy and the user @realDonaldTrump should be immediately permanently suspended from the service."
The president had more than 88 million followers on Twitter.
Facebook CEO Mark Zuckerberg also announced Thursday that President Trump's Facebook and Instagram accounts will be blocked for at least the next two weeks until Biden is inaugurated.