A New Jersey Army National Guardsman who passed away on Saturday is the first U.S. service member to die of COVID-19, the Pentagon announced Monday afternoon. 

The guardsman was a physician assistant named Capt. Douglas Linn Hickok, said the chief of the National Guard Bureau, Gen. Joseph Lengyel, shortly after the Pentagon's announcement.

“All of us in the #NationalGuard are grateful for his service to our nation, as a citizen & as a Soldier,” Lengyel tweeted. “Our thoughts are with his family & friends. All of us are likely to know people directly affected by this virus in the coming weeks.”

Secretary of Defense Mark Esper shared his condolences for the loss. Hickok had been hospitalized since March 21, the Pentagon said.

“Today is a sad day for the Department of Defense as we have lost our first American service member – active, reserve or Guard – to Coronavirus,” he said. “This is a stinging loss for our military community, and our condolences go out to his family, friends, civilian co-workers and the entire National Guard community.

The death comes three days after an Army spouse at Joint Base Langley-Eustis in Virginia died from complications believed to be related to coronavirus. 

A DoD contractor based in Crystal City, Virginia had previously died on March 22 after testing positive for COVID-19.

The number of positive COVID-19 cases in the DoD rose over 1,000 on Monday, with 1,043 total confirmed cases now involving service members, civilians, contractors, and dependents.

Esper said Hickok's death has lit a fire under DoD to help get the crisis under control as soon as possible.

“The news of this loss strengthens our resolve to work ever more closely with our interagency partners to stop the spread of COVID-19,” Esper said.

Lengyel also called for solidarity and strength in the fight against coronavirus.

“As our nation fights its greatest challenge in recent memory, we're all going to need to draw on our inner strength & resilience to win this war & comfort those in pain,” he tweeted. “We must bring our best selves every day to overcome this as fast as possible for our great country.”

Related: COVID-19 situation report: The latest coronavirus updates from the US military