National Security Council Director for European Affairs Alexander Vindman arrives for a closed-door deposition at the US Capitol in Washington, DC on October 29, 2019. Mandel Ngan | AFP | Getty Images

President Donald Trump unleashed a barrage of angry tweets Tuesday morning as House Democrats prepared to vote about their impeachment inquiry and a key National Security Council official headed to Capitol Hill to testify. Trump sent more than 30 tweets and retweets within two hours. Most of the tweets he shared were messages from his Republican allies in Congress, along with a few conservative media personalities. Nearly all of his own tweets railed against the latest moves by the Democrats, along with attacks on the witnesses called to testify in the probe, whom Trump labels "Never Trumpers." Trump TWEET Trump TWEET 2 Trump TWEET 3 Trump TWEET 4 Trump TWEET 5 Trump launched his social media bombardment ahead of scheduled testimony from Lt. Col. Alexander Vindman, a Ukraine expert on the National Security Council who listened to Trump's July 25 call with Ukraine President Volodymyr Zelensky.