Two brothers arrested in a quadruple killing in Tulsa lived in the same run-down apartment complex where the four women were found shot to death in early January, police said Wednesday. Police arrested Cedric Poore, 39, and James Poore, 32, on suspicion of murder, but did not disclose a motive for the killings. The brothers lived at the Fairmont Terrace apartment complex, where 23-year-old twin sisters Rebeika Powell and Kayetie Melchor, 33-year-old Misty Nunley and 55-year-old Julie Jackson were discovered dead by police on Jan. 7, police said. The killings, which investigators believe happened during daylight, brought attention to a troubled neighborhood in south Tulsa and raised concerns about whether residents were afraid to call in crime tips. City leaders formed a public safety group to study the issue. Investigators have refused to explain how the women knew each other or how they knew the Poore brothers. A preliminary medical examiner's report indicated all four women died of gunshot wounds to the head. Tulsa Police Chief Chuck Jordan said at a news conference Wednesday that the men would be formally charged after he presents the case file to prosecutors, hopefully by the end of the week. "These were horrific and tragic homicides," said Jordan, who refused to answer a question as to the brothers' possible motives for targeting the four women. In a statement late Wednesday, Tulsa Mayor Dewey Bartlett said he was confident in Jordan and the Police Department. "I knew they would bring in those involved with this hideous quadruple murder in very short order," Bartlett said. Misty Nunley's mother, Cheryl Nunley, wept aloud after she learned police had the suspects in custody. Wednesday would have been Misty Nunley's 34th birthday. "I've been praying I'd get good news, and this probably is the best news I could have gotten," Cheryl Nunley told The Associated Press late Wednesday. It's just been so hard with her not here today. But knowing that they caught these men is a tremendous load off my mind. Nunley previously has said that her daughter had befriended Powell and had been staying with her off and on for about a week. She said her daughter had lost touch with her family but was trying to get her life back together. Cedric Poore had been in the Tulsa jail since Jan. 22 on complaints alleging he had been speeding and driving a car with expired plates and without proof of liability insurance, according to jail records. His brother was taken into custody early Wednesday. Someone had heard from one of the women a few hours earlier, which is why investigators believe the killings happened during the day. Tulsa police said there were two slayings at the complex last year, and crimes such as break-ins and shootings, are common. The hastily formed Public Safety Intelligence Working Group met four times over the past month and produced a list of recommendations to submit this week to the City Council on ways to beef up crime-solving. Suggestions included investing in a new records management system to better share intelligence among local law enforcement agencies and exploring public-private partnerships to publicize the city's anonymous and underfunded Crime Stoppers tip line.