A firefighter was shot dead and a second one seriously injured while responding to a medical call at a home in Maryland, authorities said.
John Ulmschneider, 39, died after the shooting in Prince George's County on Friday night, fire officials said.
The firefighters were responding to a relative's call "expressing concern" about the occupant of the home, the county police department said in a statement.
As the firefighters tried to enter the home, the occupant shot them, police said. Specifics on the call were unclear, but authorities said it was medical-related.
Prince George's County police officers rushed to the Temple Hills scene and arrested the suspect.
Kevin Swain, a volunteer firefighter, was shot and is in serious condition, police said in a statement.
The family member who called 911 was also shot, but the injuries are not life-threatening, authorities said.
Ulmschneider was a paramedic and a 13-year veteran of the county's emergency medical services.
Colleagues mourned the fallen paramedic, described as a father and a husband.
"We are beginning to prepare to send our brother home," said Benjamin Barksdale, the deputy chief of the county fire and EMS department.