President Trump confirmed Ms Beckstrom’s death while on a Thanksgiving call with US service members on Thursday evening.
“Sarah Beckstrom of West Virginia, one of the guardsmen that we’re talking about, highly respected, young, magnificent person … She’s just passed away. She’s no longer with us,” he said.
Ms Beckstrom had volunteered to work in the nation’s capital over the Thanksgiving holiday, Attorney General Pam Bondi told Fox News after the shooting.
Both soldiers had been on a high-visibility patrol near the corner of 17th and I streets, an area where many office workers mill around at lunchtime.
The location of the shooting, just blocks from the White House, meant a number of law enforcement officials were quickly on the scene to treat the two victims and apprehend the gunman.
The suspect was shot four times while he was apprehended, law enforcement sources told CBS News, the BBC’s US news partner.
Officials said Mr Lakanwal came to the US in 2021.
He will be charged with three counts of assault with intent to kill while armed as well as possession of a firearm during a crime of violence, US Attorney Jeanine Pirro said on Thursday morning at a news conference, before news of Ms Beckstrom’s death.
“We are praying that they survive and that the highest charge will not have to be murder in the first degree,” Pirro added. “But make no mistake, if they do not, that will certainly be the charge: murder in the first degree.”
Attorney General Bondi told Fox News on Thursday that her office will seek the death penalty against the suspect, calling him a “monster who should not have been in our country”.
Mr Lakanwal reportedly came to the US under a programme for Afghans named Operation Allies Welcome that offered special immigration protections to Afghans in the wake of America’s withdrawal from Afghanistan.
Mr Lakanwal applied for asylum in 2024, and his application had been granted earlier this year, an official told CBS.