A man fatally stabbed one woman and wounded another in an apparently random attack in downtown Pittsburgh on Thursday, police said.

The woman died from a stab wound to the neck, said Victor Joseph, who heads the Pittsburgh Police Department's violent crimes unit. The other woman was in stable condition, he said.

Moments before the attack, a police officer was checking on a woman at a bus stop who he feared might be in medical distress, Joseph said. As he was checking on her, the assailant stabbed the woman, who later died.

The officer was not able to subdue the man before he attacked another woman who was passing by.

The officer was eventually able to get the attacker to drop his knife, and he was taken into custody. The officer then shifted his attention to aiding the women, including putting his finger on the neck of the first woman to stop the bleeding.

Joseph said investigators believe the incident was "a random act of violence." Police do not believe the victims knew each other.

Authorities said that one of the victims, who survived the attack, may have been wearing a hijab.

"At this time there is no evidence to suggest that this attack was racially or religiously motivated," the city's public safety department said in a statement.

The local chapter of the Council on American-Islamic Relations said in a statement Thursday it was in touch with police over the stabbing.

"Keeping in mind, recent deadly incidents nationwide and increased Islamophobic and anti-immigrant rhetoric, CAIR Pittsburgh is asking law enforcement authorities to investigate the possibility of a bias motive for the attack," the statement said.

Neither the suspect nor the victims were immediately identified.

The incident follows a stabbing spree Wednesday in Southern California that left four people dead and two injured, and which police there also said was random. The suspect robbed and attacked people at multiple sites in Garden Grove and Santa Ana, California, over the course of two hours, police said.