Two men have been arrested in a shooting rampage that left three people dead and terrorised a black community, and police said one of the suspects may have been trying to avenge his father's shooting two years ago by a black man.
Police identified both suspects as white, while all five victims in the rampage in Tulsa, Oklahoma, early Friday were black.
Police and the FBI said it is too soon to say whether the attacks in Tulsa's predominantly black north side were racially motivated.
Police spokesman Jason Willingham said that investigators are considering many possible motives but that based on messages posted on Facebook, revenge appeared to be a factor.
In a Thursday update on Facebook that appeared to have been written by 19-year-old Jake England, he angrily blamed his father's death on a black man and used a racial slur. He said Thursday was the second anniversary of his father's death.
"It's hard not to go off," given the anniversary and the death of his fiancee earlier this year, he wrote.
A family friend, Susan Sevenstar, said that England's fiancee killed herself in January.
"It's apparent from the posting on the Facebook page that he had an axe to grind, and that was possibly part of the motive," Willingham said. "If you read the Facebook post and see what he's accused of doing, you can see there's a link between the two of them." The Facebook page had been taken down by Sunday afternoon.
Acting on an anonymous tip and backed by a helicopter, police arrested England and Alvin Watts, 32, at a home just north of Tulsa around 2am. The two men were room mates, and officers went to their home, then followed them several blocks to another home, where they were arrested without incident, police said.
Authorities said they planned to charge them with murder and other offences.