( CNN ) -- The gunman in the Reno , Nevada-area medical center shooting that left one person dead has been identified as longtime Plumas County resident Alan Frazier , 51 , Sheriff Greg Hagwood said Thursday . Frazier had no serious run-ins with law enforcement before Tuesday 's shooting , which also left two victims injured and Frazier dead from a self-inflicted gunshot wound . Without elaborating , police said Wednesday that the attack did not appear random . Dr. Charles Gholdoian , 46 , was killed , and patient Shawntae Spears , 20 , was wounded , Reno Deputy Police Chief Mac Venzon said at a news conference . Dr. Christine Lajeunesse is in critical condition , but conscious , a spokeswoman for the city told CNN on Wednesday . Spears and Lajeunesse suffered single gunshot wounds . Spears also is in critical condition at Renown Regional Medical Center . The investigation , which includes interviews with 29 witnesses , indicates Frazier walked past the front desk to a patient exam room area and fired five rounds from his 12-gauge shotgun . He later killed himself with the weapon , Venzon said . The shooting occurred at the Urology Nevada office on the third floor of a medical building near Renown , leading investigators to believe it was n't random , Venzon said . Asked to explain , the deputy chief said the shooter passed the first and second floors , and making `` his way to the third floor of the building would indicate to me this is not a random event . '' He further said that it did not appear the shooter had a relationship with any of the victims , but the matter is still under investigation . Police do n't have a motive , but according to a statement from the City of Reno that summarized comments from Reno police Lt. William Rulla , the shooter 's focus might have been on physicians at the office . He had had surgery in 2010 and claimed he was having adverse symptoms because of it , Rulla said . As part of their investigation , detectives served a search warrant at Frazier 's home . They discovered a letter there that indicated his intent , as well as other firearms and notes suggesting the shooting was to be his final act , the lieutenant said . Kat Raco , an ophthalmic technician who works on the second floor of the Nevada Advanced Medicine building , told CNN that she heard at least two large booms and then the sound of scampering feet above her . Raco said she and others in her office were seeing patients when the shooting occurred and first thought someone or something had fallen . Police were there quickly , she said , telling them to lock the doors and not let anyone in . About 10 minutes after that , more police escorted everyone on the second floor to a catwalk between the building and a parking garage . A plainclothes officer asked questions before staff was allowed to leave about 45 minutes after the shooting . `` The police handled it in the best way possible , '' Raco said . `` They were very professional and calm . Everyone ( in the office ) stayed pretty calm . '' Raco said there are no armed guards in the building . The medical center describes itself as the only Level II trauma center in that region of Nevada and is home to the area 's only Children 's Hospital , its website says . The facility also offers the region 's largest number of clinical research trials . Last month , there was a hospital shooting in Wisconsin when police shot and wounded an armed man on the neonatal intensive care floor of a Milwaukee-area children 's hospital , authorities said . Milwaukee police had gone to the Children 's Hospital of Wisconsin to arrest the man on a felony warrant and found him holding a child in the intensive care unit , authorities said . Instead of surrendering , the man took out a handgun and fled down a hallway , prompting police to shoot him . Colorado school shooter planned larger attack , Sheriff 's Office says . Newtown shooting a year later : America reflects . CNN 's Mayra Cuevas , Eliott C. McLaughlin , Chandler Friedman and Steve Almasy contributed to this report .
NEW : Shooter left a letter indicating his intent . NEW : He had had surgery in 2010 and claimed he was having adverse symptoms . City official identifies third victim as Dr. Christine Lajeunesse . Dr. Charles Gholdoian killed , and patient Shawntae Spears is in critical condition , police say .