Anthony Naiboa never meant to be in the neighborhood. The 20-year-old Floridian had accidentally taken the wrong bus and was searching for the correct stop. But he never made it. Within moments of exiting the vehicle, Naiboa was shot and killed.

Naiboa’s murder on Thursday was the third in what Tampa police think might be a series of connected slayings. Naiboa was found dead on a southeast Tampa sidewalk within a mile of the spots where two other young bus-riders were discovered dead the previous week.

"We think they're related. Through the proximity and the time frame, they are related," Tampa interim police chief Brian Dugan said during a press conference on Friday. "There is no doubt in our minds about that."

As a child, Benjamin Mitchell moved to Tampa to live in a safe community, his aunt told Tampa’s Fox 13 news. But the safe haven turned deadly the night of October 9 —and neither police nor Mitchell’s family know why.

Mitchell, 22, was a college student and an aspiring musician: "just a really upstanding guy," Tampa Police spokesperson Steve Hegarty told the station.

Mitchell was waiting by a bus stop to ensure his girlfriend got home safely around 9 p.m. when neighbors heard at least two shots ring from the street. When they rushed to the bus stop, the neighbors found Mitchell dying on the sidewalk. He hadn’t been robbed, and had a “clean” history, police said. Investigators’ only lead was a short video of a man strolling the street around the time of the murder, his face obscured by a hood.

"I don't know if he was in the wrong place at the wrong time,” Hegarty said of Mitchell.

Two days later, less than a mile away, neighbors heard gunshots again. This time not even a surveillance camera captured anyone entering or leaving the area.

"I heard about five gunshots: pow, pow, pow, pow," neighbor Romano Whitley told Fox 13. "I came outside and I looked, I didn't see anything, I didn't hear any cars."

It would be another two days before a lawn mowing company would discover Monica Hoffa, 32, dead in a vacant field. Hoffa and Mitchell didn’t know each other, police said. The pair had little in common, besides frequenting Tampa’s bus route; Hoffa’s body was found six blocks from the city’s Number Nine bus line. The following week, Naiboa would accidentally take that same line, and end up dead.

By the date of Naiboa’s murder, police had the area on lockdown with a SWAT team nearby, K-9 patrols, and a helicopter monitoring the neighborhood, police said Friday. Still, when Naiboa stepped off the Number Nine bus on Thursday evening, the only person watching him was his killer.

Naiboa, 20, was autistic, and had recently graduated high school. He usually arrived home promptly, his family told CBS. But that evening, Naiboa had taken the wrong bus by accident. When he realized his mistake, Naiboa got off the bus and set off in the direction of the correct stop. He walked approximately 200 yards from the bus stop before an anonymous person shot and killed him.

He died 100 yards from the same sidewalk where Mitchell had collapsed. A nearby police patrol came running at the gunshots, but did not see the shooter.

“I'm convinced we are going to catch this person,” Dugan, the police chief said Fiday. “It's frustrating and it makes me angry they are able to vanish so quickly.” With three deaths in 11 days, and a killer vanishing into the shadows, Tampa police have brought on the FBI for help in the case.

“I don't know what your motive is,” Dugan said, addressing the killer. “I don't know what your problem is.”

Asked if the shootings were the work of a serial killer, Dugan said the answer was a matter of semantics. "We can call it what we want," he said. "If that brings attention to it, that's fine."

As local and federal authorities canvas the neighborhood, police are asking residents to keep their porch lights on, denying the killer the cover of darkness.

"I go from frustration to anger,'' Dugan said. "Now we have someone terrorizing the neighborhood. It's just difficult to see this happen."