HAYWARD -- A man broke into a Hayward apartment and opened fire with an AK-47 after an argument over money Tuesday morning, police said.

No one was injured in the shooting, which was reported at 6:25 a.m., and no arrests had been made, according to police.

Earlier that morning, police said the suspect visited the apartment of a 21-year-old man on the 1900 block of B Street. A fight ensued because the suspect owed money to the residents, according to Hayward police Sgt. Mark Ormsby.

A short time later, the suspect returned with the assault rifle, broke a living room window and climbed inside, as the 21-year-old man and his 21-year-old girlfriend ran to a back bedroom, Ormsby said. The suspect fired once through the living room wall, and fired another shot through the bedroom door, hitting no one, police said.

The male victim climbed out a back window and ran off, as the suspect entered the bedroom and questioned the girlfriend about where they kept their money. He then stole an undisclosed amount of cash from the living room, police said.

Police have not released a description of the shooter and said the victims have not been cooperative with the investigation. The suspect and the victims are friends, according to police.

The incident is being investigated as a home-invasion robbery.

Contact Rick Hurd at 925-945-4789 and follow him at Twitter.com/3rdERH. Contact David DeBolt at 510-262-2728 and follow him at Twitter.com/daviddebolt.