(RALEIGH, N.C.) -- Police are searching for answers after a teenager allegedly killed five people, including a police officer, and injured two others in a mass shooting along a nature trail in Raleigh, North Carolina.
The suspected shooter, a 15-year-old boy, is a relative of one of the victims killed, according to a law enforcement official briefed on the investigation.
Among the victims was Raleigh police officer Gabriel Torres, 29, who was on his way to work when he was shot and killed, according to Raleigh police Chief Estella Patterson.
The four others killed were identified as Nicole Connors, 52; Susan Karnatz, 49; Mary Marshall, 34; and James Roger Thompson, 16.
The unnamed suspect was taken into custody with life-threatening injuries, according to a memo issued by the Department of Homeland Security and obtained by ABC News. It's not clear if the suspect's injuries were self-inflicted, the memo said.
The suspect was still hospitalized in critical condition as of Friday morning, according to the police chief.
A motive is still unknown, according to Patterson, who told reporters that a five-day report will be released. She would not say what type of firearm was used in the shooting or how the suspect obtained the weapon.
"My heart is heavy because we don't have answers as to why this tragedy occurred," Patterson said during a press conference.
Officers searched the suspect’s home on Friday, according to a law enforcement official briefed on the investigation. Detectives so far have not found any social media footprint for the suspect, the official said, adding that investigators are going through handwritten material.
The shooting took place in the vicinity of the Neuse River Greenway Trail, near Osprey Cove and Bay Harbor drives in Raleigh. The crime scene spans over 2 miles. The suspect first shot two people in the streets of the neighborhood before fleeing toward the nature trail, where he opened fire, killing three more people and wounding two others, according to Patterson.
The police chief told reporters that the arrest of the suspect came after a "long standoff" and was a "team effort" by multiple agencies.
A 59-year-old was among the two shot and injured and remains hospitalized in critical condition, according to Patterson.
Raleigh police officer Casey Joseph Clark, 33, was also injured; he has been treated and released from the hospital.
A police dog was also injured and will recover, a law enforcement official said.
In a statement on Friday, President Joe Biden called for an assault weapons ban.
"We are thinking of yet another community shaken and shattered as they mourn the loss of friends and neighbors," he said. "Enough. We’ve grieved and prayed with too many families who have had to bear the terrible burden of these mass shootings."
Biden touted the bipartisan gun safety bill he signed into law in June but said "we must do more."
"We must pass an assault weapons ban," Biden continued. "The American people support this commonsense action to get weapons of war off our streets. House Democrats have already passed it. The Senate should do the same. Send it to my desk and I’ll sign it."
North Carolina Gov. Roy Cooper called the mass shooting an "infuriating and tragic act of gun violence."
"We're sad, we're angry and we want to know the answers to all the questions," Cooper said during Friday morning's press conference. "Those questions will be answered -- some today and more over time."
The Raleigh Police Department tweeted Friday afternoon, "The outpouring of love and support we have received from members of the community, our fellow law enforcement officers and first responders, as well as our local and state officials, has been truly heartening. ... The road ahead is a difficult one, but we will take it one step at a time knowing the city of Raleigh walks with us."
ABC News' Will Gretsky, Aaron Katersky and Josh Margolin contributed to this report.
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