U.S. Sen. Chris Murphy, D-Conn., ranking member of the subcommittee that funds the U.S. Capitol Police, is calling for a full investigation into how the Capitol’s security was breached so quickly in Wednesday’s attacks by pro-Trump rioters.

“I don’t know exactly what a full investigative process will look like but clearly we need to make serious changes to the way our Capitol is defended and we need to start implementing those changes now,” Murphy said during a virtual news briefing Thursday.

With the new Democratic majority in the Senate, Murphy is in line to be the chairman of the legislative subcommittee of the Senate Appropriations committee, which oversees the Capitol Police.

Murphy cast primary blame for the Capitol riot on the perpetrators, President Donald Trump and “his enablers" in Congress, but said questions remain as to how the breach occurred, what changes in Capitol security are needed and why it took so long for the Department of Defense to provide support to the Capitol Police, who “should have prepositioned more assets and requested more help.”

“Why are we spending $700 billion on the military every year if the military can’t effectively defend the United States Capitol from attack?” he said.

In a conversation with the Army secretary following the riots, Murphy said he raised the issue of whether the National Guard should be relied on to respond in such a situation.

"Unless they are prepositioned, these are people with other jobs. It takes them hours to leave their current place of employment, get into uniform and arrive at the Capitol," he said "That cannot be our plan for defending the United States Capitol against attack. There has got to be a mechanism by which we get the U.S. military to defend the Capitol within 30 to 60 minutes of an attack."

Murphy noted that the top three people in the line of succession to the presidency — Vice President Mike Pence, House Speaker Nancy Pelosi and Senate President Pro Tempore Chuck Grassley — were all in the Capitol building at the time of the attacks.

During a separate news briefing earlier in the afternoon, U.S. Sen. Richard Blumenthal, D-Conn., also called for an investigation into the response by law enforcement and the Pentagon.  

“Whether it was coordinated or not, clearly it was lax and lagging at the highest levels, and I want to know why and who was responsible,” Blumenthal said. “They should be held accountable because physical danger to individual safety was involved.”

Blumenthal noted "some instances of heroism" on the part of Capitol Police, “folks who put their lives on the line and were involved with clearing the Capitol of those protesters should be recognized.”

“But I want to know among decision makers why the National Guard was late in appearing, why the D.C. National Guard was deployed only after the Virginia National Guard made a decision to be available. The Department of Defense should be held accountable,” he said. 

Blumenthal said the investigation “should be led at the highest levels of the incoming administration by the attorney general and his team.”

Addressing “a number of concerning videos” circulating online, including one appearing to show a police officer posing for a photo with a rioter inside the Capitol, Murphy said he and other members of Congress have asked Steve Sund, chief of the Capitol Police, to “look at those videos and respond to us with explanations.”

“I think it’s very hard to look at a 30-second video or a 40-second video without context to understand what was happening at the time and what led to those actions,” he said. “From what we have been told, there was an active confrontation for over an hour outside the Capitol complex between the Capitol Police, municipal police and the protesters before they breached the building.”

Murphy said he’s also seen videos that show law enforcement officers “heroically battling to defend the Capitol.”

“We’ve got to put all this together and get a full accounting of what happened,” he said.

Sund defended his department's response, saying Thursday that officers “acted valiantly when faced with thousands of individuals involved in violent riotous actions.”

In his first public comment on Wednesday's mayhem, Sund said in a statement that rioters “actively attacked” Capitol Police and other law enforcement officers with metal pipes, discharged chemical irritants and “took up other weapons against our officers.” The siege was “unlike any I have ever experienced in my 30 years in law enforcement here in Washington, D.C.,'' said Sund, a former city police officer.

"Make no mistake: these mass riots were not First Amendment activities; they were criminal riotous behavior. The actions of the USCP officers were heroic given the situation they faced," he said.

The Associated Press reported Thursday evening that Sund is resigning as chief of the Capitol Police effective Jan. 16 after Pelosi called on him to step down.

Day Staff Writer Sten Spinella and The Associated Press contributed to this report.

j.bergman@theday.com