Outgoing Capitol Police chief Steven Sund said efforts to deploy the National Guard over last Wednesday's riots were hampered by the Pentagon and House and Senate security officials, according to an interview with the Washington Post published late Sunday.

Why it matters: Sund, who resigned over the violence, told WashPost his requests for Guard help were "rejected or delayed" six times in total — including before the Capitol Hill protest and ensuing violence began.

• Sund said he's concerned that if officials "don't get their act together with physical security, it's going to happen again" — possibly at President-elect Joe Biden's Jan. 20 inauguration.

Between the lines: Sund said House Sergeant-at-Arms Paul Irving expressed discomfort over the "optics" of declaring an emergency before the protests.

• Michael Stenger, the then Senate Sergeant-at-Arms, advised Sund to informally ask for the Guard to stand by if required by Capitol Police, according to Sund.
• Both Irving and Stenger have since resigned from their positions.
• "We knew it would be bigger," Sund told the Post. "We looked at the intelligence. We knew we would have large crowds, the potential for some violent altercations. I had nothing indicating we would have a large mob seize the Capitol."

Zoom in: When the mob broke into the main building at 2:26pm, Sund said he requested backup in a conference call to the Pentagon to "get boots on the ground."

• But Sund and others on the call say a top Army official told them that he couldn't recommend the request to Army Secretary Ryan McCarthy as "I don’t like the visual of the National Guard standing in a police line with the Capitol in the background."
• The pro-Trump mob breached the west side perimeter within 15 minutes.
• "If we would have had the National Guard we could have held them at bay longer until more officers from our partner agencies could arrive," Sund noted.
• National Guard personnel eventually arrived at the Capitol at 5:40pm, after four people had died in the violence.

The other side: The Pentagon and representatives for the House and Senate Sergeants-at-Arms did not immediately respond to Axios' request for comment.

• But Pentagon spokesperson Jonathan Hoffman said last week that based on an assessment from Capitol Police and federal law enforcement, "they believed they had sufficient personnel and did not make a request."
• Stenger declined to comment to WashPost and Irving couldn't be reached by the news outlet.

The big picture: Sund offered his resignation last Thursday, effective Jan. 16. Assistant Chief Yogananda Pittman was named Capitol Police's acting chief on Sunday.

• Senate Majority Leader Mitch McConnell (R-Ky.) said last Thursday he had "requested and received" the resignation of Stenger, who was replaced by Deputy Sergeant-at-Arms Jennifer Hemingway as acting sergeant-at-arms.
• Several lawmakers have vowed to investigate law enforcement's response to the violence.