A gunman opened fire inside a busy dental office in an apparent domestic dispute Wednesday, killing one woman dead and critically wounding three others, police said. A fourth person was grazed by a bullet.

The suspect — wearing shorts, no shirt and with a shaved head — barricaded himself inside the Family Dental Care office, police Sgt. Karl Becker said. He surrendered after a hostage negotiator coaxed him out about an hour after the shootings.

Detectives did not release a motive or identify the suspect. But the Ventura County Star newspaper reported that a dental office worker said the gunman was married to the slain victim.

In the minutes after the attack, police evacuated more than a dozen people from the dentist's office and a chiropractic office next door, including two children who witnessed the shooting.

Carley Hodgson, an X-ray technician intern working next door, said she heard three shots in quick succession and huddled in the back room with six co-workers behind a locked door for about 30 minutes.

Shawn Peloquin, a mechanic who owns an auto repair shop behind the dentist's offices, saw people running out the back and into his driveway, including a man who had a stomach wound.

Peloquin said the injured man told him that his sister had been shot several times.

Peloquin and Becky Brown, a volunteer EMT, tried to stop the bleeding by applying pressure to the wound.

Simi Valley is about 35 miles northwest of Los Angeles.