TAMPA — Tampa police blockaded a neighborhood and searched with a SWAT team and dogs for a possible serial killer Tuesday after a fourth person was shot dead for no apparent reason.

Residents of the Seminole Heights neighborhood reported hearing shots just before 5 a.m. Tuesday. Officers quickly moved in, and found the body of Ronald Felton, 60, who had been walking across the street when a gunman came up behind him and fired, interim Police Chief Brian Dugan said.

‘‘Our officers responded within seconds,’’ Dugan said, noting that enabled officers to quickly set up a perimeter around a roughly square-mile area. SWAT officers assisted by agents from the Federal Bureau of Alcohol, Tobacco, Firearms, and Explosives could be seen patrolling the streets with rifles as they moved through yards and banged on doors.

‘‘I believe that this person lives in this neighborhood,’’ Dugan added as he spoke with reporters at the scene. ‘‘And we need everyone’s cooperation; we need everyone to pay attention to what’s been going on.’’

Dugan said that until his detectives can determine otherwise, Felton’s shooting will be treated as if it’s related to last month’s 10-day spree where three people were slain. The previous three victims were alone and had gotten off a bus in the neighborhood when they were gunned downed at night. None was robbed.

‘‘This has got to stop,’’ Mayor Bob Buckhorn told a news conference on Tuesday. ‘‘We will hunt this person down until we find him.’’

Cynthia Murray told the Tampa Bay Times that Felton had been living with her near the shooting scene. She said Felton was an unemployed construction worker who volunteered Tuesdays and Fridays at the nearby food bank run by a church, which is close to where he was shot. She said he would go to the church at 2:30 a.m. to help.