Vindman reported concerns about Trump’s call to an intelligence officer and State Department official.

Colonel Vindman and Ms. Williams were the first two witnesses at a public hearing who listened in real time to Mr. Trump’s now-infamous July call with President Volodymyr Zelensky of Ukraine. Both said they were alarmed; Ms. Williams called the call “unusual and inappropriate” while Colonel Vindman said it was “wrong.”

But Ms. Williams said she told no one about her concerns, while Colonel Vindman offered new detail of what he did after the call: He told an intelligence officer and a State Department official before reporting his concerns to the security council’s top lawyer. Together, their responses contrasted with other witnesses who have said they heard nothing wrong with the call.

The July call transcript was put on a secure server to limit access and prevent leaks.

Colonel Vindman provided new details about how the reconstructed transcript of the call ended up in a secure White House server. He testified that he believed that John A. Eisenberg, the senior lawyer at the National Security Council to whom he reported his concerns about the call, intended to put the reconstructed transcript into a secure system to limit access and prevent leaks. “I didn’t take it as anything nefarious,” the colonel testified. His testimony contradicts Timothy Morrison, his former direct superior at the council, who has told lawmakers that the transcript was accidentally put on the secure system.

Trump’s requests for investigations were demands, Vindman said.

Colonel Vindman testified that he believed that Mr. Trump’s request for Ukraine to open investigations into the “2016 election, the Bidens and Burisma” — inquiries that could help Mr. Trump’s re-election chances — should be viewed as demands that were “inappropriate and had nothing to do with national security.”

Colonel Vindman also revealed a new understanding about how he conveyed to his superiors his concerns over a White House meeting on July 10 with Ukrainian officials. He said he immediately spoke to Mr. Eisenberg, adding to a similar account from Fiona Hill, who at the time was Colonel Vindman’s superior at the National Security Council.