One firefighter was killed and four others remain hospitalized after a fiery explosion took place in a house while firefighters were inside. Firefighters arrived at a home in a Washington, D.C., suburb to investigate a report about a gas smell Friday night and discovered a 500-gallon underground propane tank with a leak on the side of the residence. Shortly after they arrived, the house exploded and burst into flames, with multiple mayday calls coming from the firefighters trapped inside. Crews rushed in to try to rescue them from the debris that covered them, but one firefighter was killed and 10 others were injured, Loudoun County Fire and Rescue officials said Saturday. Four of the firefighters hurt in the blast remained in hospitals Saturday morning, according Loudoun Fire and Rescue System Chief Keith Johnson. Johnson said all four are expected to survive. A total of 11 first responders were sent to hospitals with “varying degrees of injuries” Friday night, including the one who died. He was identified as 45-year-old Trevor Brown, a volunteer with Sterling Volunteer Fire Company. Brown was married with three children and had been with the county firefighting services since 2016, Johnson said. “We lost a family member," Johnson said Saturday. "We lost one of our own. Quite frankly we’re lucky we only have one fatality. Our folks were in that house when it exploded. They did what they had to do.” Johnson said investigators have not determined the cause of the explosion, but “we can assume it was propane-related.” Two people inside the house were escorted out before the explosion and suffered only minor injuries from the blast.