New details revealed in brutal attack on Paul Pelosi.

NBC News has learned new details about the moment San Francisco police officers arrived at the home of Paul Pelosi during an alleged assault.

A top ally of House Speaker Nancy Pelosi is demanding fresh answers from the U.S. Capitol Police about security failures that led to a brutal attack on Pelosi’s husband last week, questioning the embattled agency about whether it can keep lawmakers and their families safe.

House Administration Committee Chairwoman Zoe Lofgren, D-Calif., sent a four-page letter to Capitol Police Chief Thomas Manger on Wednesday, saying the attack on Paul Pelosi raises “significant questions about security protections for Members of Congress.” The man who beat Paul Pelosi with a hammer was looking for Nancy Pelosi and later told police that he wanted to hold her hostage and break her kneecaps to make a political point, authorities said.

The searing letter lays out a series of questions for Manger and orders the agency to lay out its plans for protecting lawmakers and their families, including how they are interacting with other law enforcement agencies, how officers are trained for such situations and whether there are special plans in place to protect lawmakers in the presidential line of succession, as Pelosi is.

The letter from Lofgren, whose panel oversees the Capitol Police, comes as the beleaguered agency is still trying to rebuild after the Jan. 6 Capitol insurrection, when hundreds of former President Donald Trump’s supporters overwhelmed officers and more than 100 were injured. Threats to lawmakers have skyrocketed in recent years — almost 10,000 threats were investigated last year — and the agency has struggled to protect lawmakers, their families and the Capitol campus with limited resources.

The Capitol Police issued a statement Wednesday saying they will “fast track” the work they had already been doing to protect members outside of Washington. #WakeUpCLT