As police canvassed city streets, the mayor of Tulsa, Oklahoma, on Saturday urged residents to be on the lookout for clues -- and for one another -- after a gunman killed three people and left two others critically wounded.
"This is an event that is unprecedented in our recent history, and it is certainly one that ... we want to bring to an end very quickly," Mayor Dewey Bartlett told CNN. "The only thing in common (in the shootings) is the randomness."
According to police, the five victims were shot early Friday morning in four different locations within a "2- to 3-mile radius" of each other.
No suspect has been identified by name. While not ruling out the possibility others may be involved, investigators believe a white male traveling in a white pickup truck is the lone shooter, according to Tulsa police Capt. Jonathan Brooks.
Brooks added that police are looking into whether the shootings may be hate crimes. All of the victims are black.
Dannaer Fields, 49, died at a hospital following the first shooting, which occurred at 1:03 a.m., according to Brooks.
Three minutes later, two people were shot nearby. Both are in critical condition, but are expected to survive.
"The suspect just pulled up and asked a question about where to go," Brooks said, noting the witnesses said the gunman didn't use any racial slurs that might indicate a hate crime.
Then, just before 2 a.m., a fourth shooting incident -- like the first, a fatal -- occurred. The third person killed was found around 8 a.m. next to a funeral home in a more commercial district, though Brooks said police suspect he was shot much earlier.
"It appears all the victims were out walking or in the yard," said the police captain, noting the affected area was demographically diverse. "This (happened in) a residential neighborhood, predominantly single-family dwellings, except for the last victim."
Police say they know that an older model white truck with some rust on it was seen at three of the crime scenes. They are currently investigating whether the same weapon, believed to be a small-caliber gun, was used in all of the attacks.
A 25-person task force is on the case, with some of them spending the weekend "going, literally, door to door, and asking people if they have seen anything (and) what their opinions and observations are," according to Bartlett.
Tulsa police, which had at least 40 cruisers patrolling the impacted areas, were also getting help from the FBI and U.S. Marshals Service.
The mayor commended city residents for having "really come together," intent on helping authorities capture the killer.
"It should be concerning to all Tulsans, because we are all in this together," Bartlett said. "Some of our fellow Tulsans have been pretty violently shot, and some of them are not here today to enjoy the weekend with their families."