Morgue workers carry out a body at the scene of a fatal shooting in Hialeah
Police officers stormed his position early on Saturday and rescued two neighbours he had taken hostage.
The freed hostages emerged unharmed from the pre-dawn raid, which ended a stand-off that began late on Friday and lasted several hours, police in the Miami suburb of Hialeah said.
"We don't have a clear motive," Hialeah police spokesperson Carl Zogby said. "This was an irrational act, and many times there is no rational explanation."
Police said Pedro Vargas (42) had no known criminal history and he was described by other residents of the apartment building as a quiet man who kept largely to himself.
Neighbours said the gunman, described by the Miami Herald as a part-time graphic artist, may have been facing eviction, but police were still investigating.
The melee unfolded on Friday evening, police said, when the suspect set fire to the fourth-floor flat he shared with his mother. According to the Herald, police said Vargas started off by torching about $10 000 in cash he had withdrawn earlier from his savings account.
Two building managers, 78-year-old Italo Pisciotti and his wife, Camira (68), saw smoke pouring from the unit and ran to the flat, Zogby said.
"He came out of the door and shot both of them several times, killing them right at the scene," he said.
Vargas then went back inside his burning flat, walked out on the balcony and fired 10 to 20 shots into the street, Zogby said.
A man who lived across the street was killed as he was walking from a parking lot toward his home. Vargas also shot at arriving emergency personnel and police, hampering their efforts to aid the victims, police said.
The gunman then went to a third-floor flat, kicked down the door and shot dead a couple and their 17-year-old daughter, Zogby said.
Vargas next ran through the building, firing erratically and exchanging gunshots with police officers who swarmed to the building. Running up to the fifth floor, he took two people hostage and barricaded himself inside their flat, police said.
Gun battle
Negotiators made contact with the gunman during the night but the talks fell apart and the Swat team stormed the apartment where he was holed up at about 2am, police said.
Vargas, armed with a 9-millimetre handgun, still had about 100 rounds of ammunition left and was firing and "ready to fight" when police killed him, Zogby said.
"All this while, officers are trying to save the hostages, grab them, pull them out of the apartment while this gun battle was going on," he said.
Police said the gunman's mother was away visiting relatives in Miami at the time of the shootout, though there was some confusion over whether she was at the apartment when the trouble began.
The complex in the blue-collar, mostly Hispanic community houses about 90 families.
More than 100 police officers from Hialeah and surrounding communities responded to the situation. Some residents were in tears as the investigation continued on Saturday. Others stood on balconies and in hallways looking bewildered.
The ceiling and outside wall of Vargas's flat were charred from the fire and blood from the slain building managers stained the door. Three small red flowers had been placed nearby. Down the hall were more flowers and a heart-shaped glass ashtray with three red candles burning in it. – Reuters