It’s still not completely clear how Officer Brian Sicknick was fatally injured during the Capitol riot but one report said he was hit in the head with a fire extinguisher. He went back to his office after the attack where he collapsed. He was taken to the hospital but died the following night. Yesterday CNN reported that investigators trying to identify those directly responsible have been unable to do so thus far:

Investigators are struggling to build a federal murder case regarding fallen US Capitol Police officer Brian Sicknick, vexed by a lack of evidence that could prove someone caused his death as he defended the Capitol during last month’s insurrection.

Authorities have reviewed video and photographs that show Sicknick engaging with rioters amid the siege but have yet to identify a moment in which he suffered his fatal injuries, law enforcement officials familiar with the matter said.

Starting last night, Sicknick’s fellow officers as well as members of congress and President Biden paid final respects to him in the Capitol rotunda. Here’s the solemn scene as his remains were brought in:

U.S. Capitol Police Officer Brian Sicknick Arrival & Lying in Honor in U.S. Capitol Rotunda pic.twitter.com/QcGWQXSQZP

— CSPAN (@cspan) February 3, 2021

President Biden and the First Lady paid their respects. They both put their hands over their hearts and then Biden crossed himself.

Pres. Biden and first lady Jill Biden pay respects to Brian Sicknick, the Capitol Police officer who died from injuries suffered during last month's violent siege, as Sicknick lies in honor at the Capitol Rotunda. https://t.co/iDuJT62CBR pic.twitter.com/PKxnuY9mcA

— ABC News (@ABC) February 3, 2021

Today, the flag over the Capitol was at half staff:

Flag at the Capitol is at half staff as Officer Sicknick is honored inside. pic.twitter.com/wScsobT8mw

— Samantha Manning (@SamManningNews) February 3, 2021

Speaker Pelosi spoke at a memorial service attended by his family:

Capitol Police Officer #BrianSicknick lived a life of honor, service, and sacrifice that will never be forgotten.

All who knew Officer Sicknick loved and respected him for how he treated others and for his love of country. Today, his country honors him and mourns his loss. pic.twitter.com/1hBfMVL4xN

— Georgie (@jorge_aguilarDC) February 3, 2021

One of his fellow officers saluted:

A Capitol Police Officer pays her respects before a ceremony memorializing US Capitol Police Officer Brian Sicknick as he lies in honor in the Rotunda of the Capitol.

📷 Anna Moneymaker / Getty pic.twitter.com/sPlBzEZks6

— NBC News (@NBCNews) February 3, 2021

Officer Brian Sicknick Lies in Honor In U.S. Capitol … from last night pic.twitter.com/sSWak9iy1Q

— Howard Mortman (@HowardMortman) February 3, 2021

There were also a lot of tributes posted on social media:

Today we honor the life, courage, and sacrifice of fallen United States @CapitolPolice Officer Brian Sicknick.

Thank you for defending us.

Thank you for defending the Capitol.

Thank you for defending our Democracy.

You will never be forgotten. pic.twitter.com/t9bouhUqU8

— Senate Republicans (@SenateGOP) February 3, 2021

Very moving tribute to Officer Brian Sicknick who was killed in the Capitol Hill riots on January 6. He was a true hero, serving his country as a police officer and a member of the Air Force. My prayers are with his family and friends. May he rest in peace.

— Lindsey Graham (@LindseyGrahamSC) February 3, 2021

Officer Brian Sicknick gave his life protecting the U.S. Capitol and the lives of those of us inside of it. But most importantly, he gave his life protecting our democracy. He is a hero—our Capitol Police officers are heroes. Rest in peace—we will never forget your sacrifice. pic.twitter.com/ofEDgl6cMk

— Senator Mitt Romney (@SenatorRomney) February 3, 2021

When a violent mob desecrated the Capitol, Officer Sicknick met it with bravery, devotion, and unmatched courage. His heroism not only helped save lives, it valiantly protected every American’s way of life.

Congress and the entire nation owe him a debt of gratitude. pic.twitter.com/y64vVcZJ1P

— Kevin McCarthy (@GOPLeader) February 3, 2021

This may be the last thing in Washington that people on both sides of the aisle can agree on:

We honor Officer Brian Sicknick: a New Jersey native, an Air National Guard veteran, and a twelve-year member of the Capitol Police Force.

A peacekeeper, not only in duty but in spirit.

His heroism helped save lives and defend this temple of our democracy. pic.twitter.com/MsLiYoy4Ca

— Chuck Schumer (@SenSchumer) February 3, 2021

An honor to be one of many paying respect today for a hero

Officer Brian Sicknick remembered as hero who died defending the U.S. Capitol https://t.co/ddFepKuZFY

— Amy Klobuchar (@amyklobuchar) February 3, 2021

Today we shared a solemn moment of remembrance of a hero who gave the greatest devotion possible to the country he loved. We owe Officer Sicknick a debt that can never be repaid. pic.twitter.com/jRyDwqJAlh

— Sen. Cory Booker (@SenBooker) February 3, 2021

After the ceremony was over, Sicknick’s remains were removed from the Capitol and taken for burial in Arlington Cemetery. Police and fire fighters escorted him and lined his path:

APD participated in the memorial service for fallen U.S. Capitol Police Officer Brian Sicknick. Our officers rendered honors for Ofc. Sicknick, and joined the escort from the U.S. Capitol to Arlington National Cemetery. Our prayers are with his family and friends. pic.twitter.com/R8dbUp3Ssw

— Alexandria Police (@AlexandriaVAPD) February 3, 2021

Public safety is one big family. When we lose one, we all mourn. RIP @CapitolPolice Officer Brian Sicknick. @ffxfirerescue @AlexandriaVAFD @FortMyerFire @ArlingtonVaPD @VSPPIO pic.twitter.com/h8MJplN6A8

— Arlington Fire (@ArlingtonVaFD) February 3, 2021

As the funeral cortège of fallen Capitol Hill Police Officer Brian D. Sicknick crossed the Memorial Bridge towards his final resting place at Arlington Cemetery, #DCsBravest Fireboat 1, the John Glenn, honored him with a water borne salute. RIP. pic.twitter.com/Qi0fFfaMf1

— DC Fire and EMS (@dcfireems) February 3, 2021

Rest in peace, Officer Sicknick.