WASHINGTON (NEXSTAR) — Senators held their first public hearing on Tuesday regarding the Jan. 6 attack at the U.S. Capitol.

Lawmakers on both sides of the aisle pressed for answers on how to prevent anything like it from happening again, and grilled those who were in charge of protecting the Capitol.

“We properly planned for a mass demonstration with possible violence. What we got was a military-style coordinated assault on my officers and a violent takeover of the Capitol building,” former U.S. Capitol Chief of Police Steven Sund said.

Sund resigned from his position as the head of Capitol Police on Jan. 16, 10 days after the Capitol breach. House Speaker Nancy Pelosi, D-Calif., had called on him to step down the day after the riot.

During the hearing, Democratic Georgia Sen. Jon Ossoff asked who has “ultimate responsibility” for security at the U.S. Capitol complex. He also wanted to know why the National Guard wasn’t called in immediately to assist.

“You, in fact, anticipated there might be some need based on intelligence your department was seeing,” he said.

Sen. Mark Warner, D-Va., said part of the problem was Washington, D.C.’s mayor doesn’t have the needed authority.

“Shouldn’t the mayor of the District of Columbia have the ability to do that without all the additional hurdles they need to go through in terms of federal checklists?” Warner said.

The National Guard is still at the U.S. Capitol as razor wire-topped fencing surrounds the perimeter. Republican Florida Senator Rick Scott wants to know why.

“There’s no public information about why we have all these National Guards here,” he said. “I mean, does that surprise you?”

Sund replied that, “it’s the facts of what occurred on Jan. 6 – unprecedented insurrection.”

“We need answers right away to be able to make decisions going forward,” Sen. Amy Klobuchar, D-Minn., said.

Additional hearings about the Jan. 6 attack are already planned. Senate Majority Leader Chuck Schumer, D-N.Y., says senators will be briefed on the future of capitol security later this week.

“It’s our solemn duty to prevent a day like Jan. 6 from ever, ever being repeated,” he said.