(Image source from: Chicagotribune.com)

One male who was among the four people shot Thursday afternoon in a Colorado business complex has died, while his mother and brother were in critical condition, police said.

Another male victim was shot in the complex's parking lot and is expected to survive, authorities said.

Police have arrested a suspect. The motive for the attack in Westminster, Colorado, is unknown. Authorities were expected to release the suspect's identity later Friday.