Thornton, CO, police have arrested a 47-year-old suspect in the apparently random Walmart shooting in which a man almost casually shot two men and a woman, killing them, before turning around and walking out of the store Wednesday night.

Scott Ostrem, 47, was arrested at around 8 a.m.

Police searched Ostrem’s last known address, in the 7100 block of Samuel Drive in Denver, on Thursday morning, Thornton police spokesman Victor Avila said at a 9 a.m. news conference. Ostrem was not at home.

Ostrem was stopped and arrested without incident, Avila said. A loud noise reported by bystanders was a SWAT unit’s flash-bang grenade, used as a distraction during the arrest, Avila told the Denver Post.

Ostrem allegedly used a handgun to shoot the three people in the Walmart Wednesday evening, Avila said.