A doctor, a newly graduated pharmacist are among three people killed after a gunman opened fire at a hospital in Chicago.

A police officer was also killed in the shooting.

According to the BBC, the gunman in the Chicago Hospital shooting was seen arguing with the doctor, Tamara O’Neal, who he had been in a relationship with, before shooting her and turning his gun on others.

The shooter, who has not been named, also died but it is not clear if he was killed by police or took his own life.

Mayor Rahm Emanuel said the attack “tears at the soul of our city”.

“It is the face and a consequence of evil,” he said, adding that the three victims were “all going about their day, all doing what they loved”.

The shootings began with a row in the Mercy Hospital car park between the gunman and Dr O’Neal at about 21:00 GMT on Monday.

When a friend of the doctor’s tried to intervene “the offender lifted up his shirt and displayed a handgun”. Chicago Police Superintendent Eddie Johnson said.

As the friend ran for help, gunfire broke out. One witness, James Gray, told reporters he saw Dr O’Neal fall to the ground and then the gunman “stood over her and shot her three more times”.

When police arrived, the gunman then moved into the hospital, shooting at random and killing pharmacist Dayna Less who was getting off an escalator at the time.

In an exchange of fire with the gunman, police officer Samuel Jimenez was killed. A second police officer avoided injury after a bullet fired in his direction became lodged in his gun in his holster.