ST. LOUIS (CBS NEWS) -- St. Louis police have arrested a man suspected of fatally shooting his ex-girlfriend and her new boyfriend then wounding a police officer in subsequent gunfire.

Police Chief Sam Dotson said early Thursday that the shooting overnight also wounded a man who is believed to be related to the woman.

The gunfire erupted late Wednesday after a confrontation on the porch of a St. Louis home. Dotson said the suspect pulled out a gun and the boyfriend was shot and killed during a struggle over the weapon.

The chief said the woman and the second man fled, but that the suspect shot them both. The woman was killed and the man was wounded. He was taken to a hospital where he is in critical but stable condition. The names of the victims haven't been released.

When officers arrived, the suspect fired at them. One shot struck a police car and another ricocheted and grazed an officer in the leg. The officer who was struck returned fire but didn't hit the suspect. The officer was treated at the scene.

The suspect fled but was captured a couple of blocks away and taken into custody.