(CNN) -- A man has been arrested in connection with this week's quadruple murder -- in which one victim was a toddler -- in the Mattapan neighborhood of Boston, Massachusetts, officials said Saturday.
Boston Police Commissioner Ed Davis said police arrested 35-year-old Kimani Washington Friday night in Manchester, New Hampshire on outstanding warrants for two counts of unlawful possession of a firearm, unlawful possession of ammunition, receiving a stolen motor vehicle, possession of marijuana with the intent to distribute and using a motor vehicle without authority.
He has not been charged with murder.
Davis declined to comment on whether police think Washington may have been the shooter in this case. He also refused to say whether police have any other suspects.
On Tuesday, police responded to 911 calls about a shooting and found three adults dead at the scene. A young child was rushed to a local hospital where he was pronounced dead shortly after arrival.
The shooting's fifth victim, an adult male, remains in critical condition at an area hospital, Davis said.
The victim reportedly told authorities that his rental vehicle was taken by a suspect and provided officers with a vehicle description. Police later saw the vehicle and observed Washington around it.
He was questioned, but initially released due to insufficient evidence to hold him.
Further investigation showed the vehicle was the one taken from the shooting scene, Davis said. Police officers went to Washington's last known address and turned up two firearms, ammunition, a scale and marijuana.
Davis declined to explain exactly how police tracked Washington to New Hampshire except to say they were following up on a tip and that they checked several addresses.
"The investigation remains active," he told reporters Saturday. "We have much work to do, but we are confident in our efforts to bring this case to justice."
Suffolk County District Attorney Dan Conley said Tuesday that the shooting was not random. The victims were found lying in the street -- one of them naked.
Earlier this month, a Domino's Pizza delivery man was murdered delivering pizza to a vacant home in Boston where three men stabbed him multiple times.
Since January there have been 52 homicides, compared to the 40 homicides in the same period last year, according to Boston police.
"Today should serve as a warning to all those who seek to harm others," said Mayor Thomas Menino. "Our offices will not rest until you are hunted down, captured and locked up."