Six people have been killed during a bloody day on the streets of Philadelphia.

The violence began Tuesday afternoon when police say a man randomly stabbed three people, killing one man and sending two others to the hospital. The suspect was taken into custody, but has not been charged.

A few hours later, investigators say gunfire broke out, leaving one man dead and another in critical condition.

Over the next several hours, police say four more men were killed in four separate shootings.

No arrests have been made in any of the shootings.

All of the killings happened in different neighborhoods, and police aren't saying whether any of them are connected.