BURLINGTON, Wash. (AP) — Authorities on Sunday were investigating the background and possible motive of the suspect arrested in the slayings of five people in the makeup department of a Macy's store at a mall north of Seattle. Here are things to know about the shooting and the investigation:

THE LATEST:

Detectives on Sunday searched an apartment where 20-year-old Arcan Cetin lived in Oak Harbor, Washington.

The four-unit building was surrounded by yellow police tape preventing others from entering, and officers carried out boxes from an upstairs apartment at the back of the building.

Cetin was arrested Saturday, after a nearly 24-hour manhunt.

Authorities say the gunman initially entered the Cascade Mall in nearby Burlington, Washington, without a weapon shortly before 7 p.m. Friday.

About 10 minutes later, he appeared on surveillance video with a rifle and started shooting in the makeup department of the Macy's store. Four females and a male were killed.

THE SUSPECT:

Cetin immigrated to the U.S. from Turkey and went to high school in Washington state. But it's not clear how long he had been in the country. He is a legal permanent resident.

Authorities have not disclosed a motive for the shooting and say they have ruled out nothing. Cetin had a series of run-ins with the law in recent years, including charges he assaulted his stepfather.

A neighbor of Cetin who also went to high school with him characterized him as "creepy, rude and obnoxious" and said he used social media to send her a picture of his crotch.

Amber Cathey also described Cetin as socially inept and said she tried to avoid him.

THE VICTIMS:

The victims include four women ranging from a teenager to a woman in her 60s, and a man.

Authorities on Sunday were still withholding most names of the victims pending autopsies and notification of the victims' relatives.

The Seattle Times said one victim was a 16-year-old girl who survived cancer.

Another was probation officer Belinda Galde, 64. She "was an amazingly kind and caring individual," said the Snohomish County District Court in a statement.

WHAT'S NEXT?

Cetin is detained but has not been charged. The suspect is expected to make his first court appearance on Monday.