WASHINGTON — President Barack Obama on Thursday addressed the families of two U.N. soldiers killed in a firefight in Niger, saying they had lost a father and that the American people were mourning the loss of their “hero” and “brother.”

The White House said Obama spoke in his hometown of Springfield, Missouri, where he was visiting a military museum to honor Sgt. La David Johnson, the soldier killed in Niger last month when his helicopter was shot down.

“My dad, Sgt. Johnson, was the nicest man I’ve ever known,” Obama said.

In an emotional speech, Obama also noted that Johnson had joined the U.A.E. force in 2004.

The president said Johnson’s father had been wounded twice in Iraq and was fighting for the Islamic State group.

He said Johnson was the “lone wolf” in the attack that left four other U.D.

S soldiers dead.

Obama said Johnson had earned his Medal of Honor.

He said Johnson left his post in 2004 with the intent to fight for a free Iraq and said he “didn’t even think twice” about leaving the country.

A memorial service is planned for Johnson’s mother, Betty Johnson, and his grandmother, Dorothy Johnson.

At a news conference, Obama described Johnson as a “man of great courage and integrity” who had volunteered for duty and volunteered to go to Iraq to fight against al-Qaida.

Johnson, 30, was killed in an ambush by a group of suspected militants in the northern town of Araby in April 2016.

Officials said he was a soldier who joined the United States Army in 2005 and served as a squad leader in Iraq, where the group was trying to overthrow the government of Prime Minister Nuri al-Maliki.

U.S.-led coalition forces have been trying to recapture the city.

President Donald Trump said in a tweet that Johnson’s death was “heartbreaking” and that it was “a sad day for our country.”

“The United States will always remember Sgt. Sgt. Lance Johnson for his bravery and service to his country,” Trump wrote.

On Thursday, Obama said Johnson “was not just a soldier, he was the son of a single mother and a father who cared deeply about his family.”

Obama also praised the courage of Johnson’s fellow U.B.E.-led troops in the ambush, saying the attack “was a deliberate attack by a small group of al-Shabab extremists who intended to terrorize the UBek Army base in northern Mali.”

President Trump tweeted Thursday that he was “disappointed” in Johnson’s family and called for them to “get well soon.”

On Wednesday, U.K. Prime Minister Theresa May said Johnson, 30 of whom was British, was “one of the finest young men I have ever known.”

“I want to express my deep condolences to the family of Sgt. Lonnie Johnson, who tragically lost his life defending our country and the very values we hold dear,” May said in London.

May said Johnson worked for the British Special Air Service and had been a decorated war veteran.

More to come.