Police are still searching for the suspect in the shooting of three people inside the Monroeville Mall near Pittsburgh in Pennsylvania on Saturday evening.

Lieutenant Andy Schurman of the Alleghany County Police said about two shots were heard inside the mall, adding authorities have yet to determine the motive for the attack.

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A Monroeville police media release identified the suspect as a black male, in his late teens and about 5-foot-7 tall. Witnesses said he was wearing a dark shirt and pants. Police declined to disclose any other information on the suspect.

An official investigation is underway, police announced. Authorities were pouring through the mall's security video as part of their investigation.

Monroeville police said the gunman zeroed in on one particular male, who suffered serious injuries. The other two victims were apparently mere bystanders, said Police Chief Doug Cole.

The male bystander also sustained serious injuries while the other -- a woman -- has light injuries. Authorities said the two appeared not to be linked with the target, in a media briefing on late Saturday evening.

All three victims were rushed to the Forbes Regional Hospital's Trauma Center.

As a matter of procedure, authorities said the emergency room was briefly locked down while the victims were being treated.

A witness said he saw a young male in a group wielding a black gun fire at least six shots at another bunch of young people. The shots triggered panic inside the mall, he added.

The shots were fired inside the Macy's store at the Mall, sending people indoors running. Police searched store to store for the suspect inside the mall, which closed for the evening.

As shots rang out, witnesses heard people screaming and saw teenagers making a beeline for the exit.

The mall bans weapons, with a code of conduct that prohibits the display and carrying of all kinds of arms except those in the possession of law enforcement officers.