Sen. Martin Heinrich grew frustrated with the refusal of intelligence officials to answer questions related to the firing of former FBI Director James Comey and the probe into Russian interference into the 2016 election.

The New Mexico Democrat questioned why McCabe wouldn’t discuss his conversations with Comey in the public hearing, saying it would not be appropriate, instead deferring to the ongoing special counsel investigation into Russian interference in last year’s election. McCabe repeatedly said he would let Comey speak for himself.