According to Reno Police Department, the incident began shortly before 7:00 p.m. Tuesday (0300 GMT Wednesday) with the suspect, identified only as a man in his 20s, opening fire from the eighth floor of the building and continuing to shoot for more than 20 minutes, Xinhua news agency reported.
Responding to the incident, police, a SWAT team and the Washoe County Sheriff's helicopter barricaded the shooter in the building along with the hostage and closed the city's downtown, where many casinos are located, till midnight.
The local KOLO TV station reported that the suspect was shot by police and died on the way to the hospital. Other reports said it could not be determined if the man had been shot by police or the death was self-inflicted.
"Thankfully no reports of injuries to citizens or officers or deputies," Reno Police tweeted after the incident, without providing details about the shooter or his motive.
The TV station also reported that 64-year-old Stephen Paddock, the Las Vegas mass shooter who killed 58 concert-goers before turning the gun on himself, owned a unit in the condominium complex.