The NYTimes has it in this video from the A.P., but I don't see many others stressing this part of the Pittman testimony, which seems to me of utmost import and which I heard on NPR earlier today .

She said they knew of intel about the likelihood of violence by extremists, and "heightened security", implying that they could handle that. 

She says what they did not prepare for was large number of "everyday Americans" turning into to an angry mob, implying that one cannot predict a crowd of everyday Americans turning into a mob because they are angry and desperate.

I could not find a way to embed the video, here is the link, it is helpful to hear it in her own intonation

"Capitol police were unprepared for the scale of 'mob mentality'"

and here is

TRANSCRIPT

1:06/1:46

Capitol Police Were Unprepared for Scale of ‘Mob Mentality,’ Chief Says

Yogananda D. Pittman, acting chief of the Capitol Police, told a House panel on Thursday that officers were unprepared for the scale of the Jan. 6 Capitol attack, and were uncertain of when to use lethal force.

The department was not ignorant of intelligence indicating an attack of the size and scale we encountered on the 6th. There was no such intelligence. Although we knew the likelihood for violence by extremists, no credible threat indicated that tens of thousands would attack the U.S. Capitol. The department also did not ignore intelligence that we had, which indicated an elevated risk of violence from extremist groups — to the contrary, we heightened our security posture. There’s evidence that some of those who stormed the Capitol were organized. But there’s also evidence that a large number were everyday Americans who took on a mob mentality because they were angry and desperate. It is the conduct of this latter group that the department was not prepared for. The department did face some operational challenges that we are addressing. For example, the Capitol lockdown was not properly executed. Some of the officers were unsure of when to use lethal force, our radio communications to officers were not as robust and we are ensuring that our incident command system protocols are adhered to going forward. And re-implementing training in those respective areas. We are addressing those operational challenges, but I want to make clear that these measures alone would not have stopped the threat we faced. To stop a mob of tens of thousands requires more than a police force, it requires physical infrastructure or a regiment of soldiers.

I "get her excuse because she is thinking 9/11 or Oklahoma bombing style, that the true danger is from organized extremists. And that everyday Americans are respectful of their main buildings of government and not expected to mob around them.

BUT I also know NYPD operates on the presumption that ANY large crowd can turn into a mob. I.E.this is why they have long corralled New's Years Eve revellers in the Times Square area into little separated squares of like 50 for blocks surrounding, it is not as it appears on teevee, that is faked to look like a large throng. They usually do not allow large crowds, protesting or something else! This is why I tended to side with cops when with huge "BLM" demonstrations (actually led by pros from Brooklyn) when the did things like kettle protesters or react when the broke curfew or tried to break their line. You don't want a protest turning into a mob, which can easily be done with the right agitation by those who know how to incite one. In NYC, we do have a history to look at what happens when a protest turns into a mob that overwhelm cops, stuff like lynchings etc... They know that they need to be the ones to have some modicum of control if large crowds or all might be lost.

I also found this at Axios very helpful, especially as it has available a PDF text of her prepared remarks submitted before she testified:

Feb 24, 2021 - Acting Capitol Police chief: Officers were unsure of lethal force rules on Jan. 6

By Ursula Perano

I looked for, but couldn't find, a full transcript from the testimony today with Q&A, it seems to take a day, as I did find that of the day before  

Senate Hearing on January 6 Capitol Attack Transcript February 23

they have her picture at the top mistakenly (or is that Mendoza?), she did not appear on Feb. 23, but they have the full transcript of all the other guys being grilled

so probably tomorrow.