A sheriff’s deputy was shot and killed on Friday evening in Eustis, Fla., while officers were responding to a report of an altercation in a neighborhood, the police said. Two people whom the police described as assailants were found dead inside a house.

The sheriff’s deputy was killed and another was injured when they entered the house at 7:45 p.m. in the Orlando Hills neighborhood of Eustis, a city north of Orlando, according to John Herrell, a spokesman for the Lake County Sheriff’s Office, where the deputy worked.

Additional deputies were met with gunfire, and one was injured, when they entered the house to rescue an officer who had entered earlier and was trapped, Mr. Herrell said. The trapped officer was later pronounced dead.

The officers found two civilians dead and a third with gunshot wounds when they entered the house, Sheriff Peyton C. Grinnell of Lake County said at a news conference early Saturday, referring to all three as assailants. It was unclear how the two civilians had died, he said, and the injured person was taken to a hospital.

Firearms were found in the house, and there were no suspects at large, Mr. Herrell said.

All three sheriff’s deputies who were shot were taken to hospitals, and one was pronounced dead just before 1 a.m., he said, adding that the dead deputy’s name would not be released immediately.

The episode was under investigation by the Florida Department of Law Enforcement, according to Mr. Herrell.