Lieutenant Mike Hawley of the state's Island County sheriff's department said he saw Arcan Cetin in Oak Harbour, Washington, from a patrol car and immediately recognised him as the suspect.

Lt Hawley told a news conference that his office had received information that Cetin, 20, from Oak Harbour, was in the area. He said Cetin, 20, was unarmed, adding: "He said nothing. He was kind of zombie-like."

A gunman opened fire at the Cascade Mall in Burlington on Friday night, killing four women and a man before fleeing.

Police staged a massive search over more than 20 hours for the suspect, initially described by witnesses as a young Hispanic man wearing black.

Authorities had said that a rifle had been found at the shooting scene.

The motive for the shooting at the mall, about 60 miles north of Seattle, was unknown. The FBI was assisting local authorities, but said there was no evidence pointing to terrorism.

Dozens of people attended a prayer service for the victims on Saturday night at Central United Methodist Church in Sedro-Woolley, Washington.

The Rev Cody Natland lit five candles on a table in front of the church, one for each victim.

One of the shooting victims was 16-year-old Sarai Lara. Her mother Evangelina Lara said she had survived cancer and was a happy student, according to The Seattle Times.

Ms Lara said she was shopping at mall with Sarai and her younger sister, but they split up, with Sarai going to Macy's looking for trousers.

News of the shooting spread through the mall and Ms Lara tried to find her daughter but was unable to do so.

It was confirmed at 2am on Saturday that Sarai was among the five people killed.

Lt Chris Cammock of Mount Vernon Police Department said Cetin, who is expected to appear in court on Monday, was from Turkey but a "legal, permanent resident of the United States".

Authorities said he had a previous arrest for simple assault.