Image copyright Phoenix Police Department Image caption Phoenix Police Department released this sketch of the suspect

Police in the US state of Arizona say a single suspect may be responsible for a series of shootings that have left seven people dead.

The first attacks were reported in March when two men were shot while walking outside; both survived.

The last incident was reported on 12 June when three women were shot and killed outside a home in west Phoenix.

All of the shootings occurred at night, and the victims appear to have been targeted at random.

A witness to one of the shootings helped detectives develop a sketch of the suspect.

Police described the suspect as a white or Hispanic man between 20 and 30 years old. He may have an accomplice, police said.

"Someone out there knows who did this," Phoenix Police Chief Joseph Yahner said. "We need our community to help us solve these cases."