A Richfield man has been charged with second-degree murder after allegedly driving his sport utility vehicle into the ex-boyfriend of a woman he was dating, St. Paul police say.

The victim, David Ramirez, 46, of St. Paul, was struck and killed while standing in a North End area street early Tuesday, talking to the woman whom both men knew.

Moises A. Nieves, 36, told police that he was just trying to protect the woman from Ramirez, who he says forced the woman to have sex with him on previous occasions, according to the criminal complaint filed against Nieves Thursday in Ramsey County District Court.

But police spokesman Peter Panos said the woman and ex-boyfriend still were friendly, leading police to doubt the suspect's claims about the forced sex, and to see a different motive behind his actions: "He wasn't happy that the ex-boyfriend was talking to the girlfriend," Panos said.

Both Nieves and the woman, who had been sitting in a separate sport utility vehicle, left the scene after Ramirez was struck. She told police that she'd "blacked out" and when she awoke she drove home.

Ramirez was dead by the time a passerby came upon the body about 5 a.m. Tuesday.

While the woman was not believed to have any role in the hit-and-run accident, Panos said that he believed investigators were looking into the question of whether she should have stayed to help the ex-boyfriend.