Three fallen Baltimore firefighters are being honored for their heroism after they were killed while responding to a blaze in a vacant home earlier this week.

Baltimore Fire Lt. Paul Butrim and Firefighters Kelsey Sadler and Kenneth Lacayo died in the line of duty Monday while responding to an early morning fire that devolved into a partial building collapse on South Strickler Street. 

Butrim, Sadler and Lacayo became trapped inside the three-story row house with another fellow firefighter, John McMaster, whose condition had improved from critical to fair as of Tuesday afternoon. 

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"From this moment, we will honor those we lost today, for their bravery, their courage, their love for helping others and the respect they had for the Baltimore City Fire Department," Chief Niles. R. Ford said in a statement late Monday. 

Ford said Tuesday that McMaster was "conscious and alert." 

Speaking to local affiliate FOX Baltimore on Tuesday, Maryland State Fire Marshal Brian Geraci said the Maryland Fire Service was "heartbroken." 

"It’s a tragic loss for all of us, because we’re family," he said, sometimes fighting tears. "And we lost a lot of family yesterday."

Firefighter Lacayo, who was also a paramedic, was a life member of the Wheaton, Maryland, Volunteer Rescue Squad, which he joined in 2011 and "steadily joined through the ranks," according to a Facebook post from the squad. 

He was a founding member of the squad’s Honor Guard and received commendations for work as a first responder in 2015, 2016 and 2018, the Wheaton Volunteer Rescue Squad, Inc. said.  

"His exceptional skills as a firefighter and paramedic were matched by his bright smile and his unfailing good nature," the squad added. "He was dearly loved by his fellow WVRS volunteers and will be greatly missed."

The group started a GoFundMe page to raise money for Lacayo’s family, and for funeral arrangements. As of Tuesday afternoon, the group had raised more than $21,000 of their $50,000 goal. 

A loved one did not respond to Fox News Digital’s request for comment on Tuesday.

Firefighter Sadler, also a paramedic, "wouldn’t take crap from anybody," her friend Tracie Martinek told the Baltimore Sun. Martinek said Sadler became known as "the beast." 

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Martinek said the pair worked together at the Jacksonville Volunteer Fire Company, which confirmed that Sadler had served as a paramedic there "for several years." 

"Everyone thought she was unapproachable until you got to know her," Martinek told the outlet. "Once you got to know her she was the sweetest person ever and would give the shirt off of her back."

She described her friend as someone who loved her family, including her pitbull, and was a "foodie," according to the report. 

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As for Butrim, the fire lieutenant boasted 16 years with BCFD, according to Firehouse Magazine. The publication honored Butrim as one of its annual Award of Valor honorees in 2015, after he pulled a child from an apartment fire and gave the victim mouth-to-mouth resuscitation until medics could arrive. 

The magazine honored him for his "great bravery in the face of dangerous conditions."

On Monday, Maryland Gov. Larry Hogan announced that he had ordered flags be lowered to half-staff in honor of the fallen firefighters. 

"Our hearts are broken for the entire Baltimore City Fire Department," he said, in part. "Each and every day, our firefighters and first responders answer the call and are ready to run into danger – this is our worst nightmare."

Baltimore Fire Fighters Local 734 and Baltimore City Fire Officers Local 964 created a GoFundMe page for those interested in raising money for the injured and fallen Baltimore firefighters.