Arcan Cetin, 20, is facing five counts of first-degree murder, according to Skagit County jail records. He will appear Monday in the county's district court.
Cetin, held in Skagit County jail on Sunday, has not been formally charged, according to Sgt. Mark Francis, a state patrol spokesman.
Four women and one man died in the shooting Friday night at a Macy's store at the Cascade Mall in Burlington, north of Seattle. The victims' identities have not been released. Cetin was taken into custody
Saturday night after a nearly 24-hour manhunt, authorities said.
"We feel confident we have the shooter," Francis told reporters. "Whether or not anyone else was involved, that will be determined."
Authorities arrested Cetin as he walked down the street near his home in Oak Harbor, Washington.
When officers confronted Cetin, he did not run, said Lt. Mike Hawley of the Island County Sheriff's Office. Instead, Cetin froze and complied, Hawley said.
"He said nothing," Hawley said.
Francis said the suspect was "calm and collected last night when he was arrested" and that he has been interviewed.
Cetin emigrated from Turkey and is a legal permanent resident of the United States, authorities said. It's unclear when he moved to the United States.
In its initial alert about the suspect Friday night, the state patrol described him as "Hispanic." Asked whether that detail delayed the investigation, Francis said it was possible.
State authorities said it's too early to rule out terrorism or any other motive because their investigation is in its preliminary stages. Before the suspect's arrest, an official with the FBI had told reporters there was "no evidence at this time" of a link to terrorism.
Francis said Cetin has an ex-girlfriend who worked at a Macy's but it is not known if it was the Macy's at Cascade Mall. So far, authorities haven't been able to find any link between the suspect and the victims.
Authorities say Cetin walked into the mall, about 65 miles north of Seattle, and opened fire with a rifle Friday night. They say he walked in without the firearm and left the weapon at the scene before he fled, sending more than 24 law enforcement agencies on a manhunt
across the state.
Authorities say they are trying to figure out where he got the weapon.
Authorities collected evidence from the mall overnight Friday and all day Saturday as the bodies were removed. Eventually, they identified his vehicle by matching information received from a tip with surveillance footage obtained from local business.
Authorities declined to comment on the type of weapon used or Cetin's mental health, citing the ongoing investigation. They did, however, say Cetin had been arrested once in the past year, for simple assault.
Burlington Mayor Steve Sexton called the shooting a "devastating loss" of five treasured members of the small community.
"That was us in that mall last night --any one of us at any time," Sexton said. "It changed those families forever. ... It changed our community forever."
Suspect to appear in court Monday