A gunman shot two people in a Costco parking lot Monday afternoon in Southern California before turning his weapon on himself, police said, the second deadly shooting at one of the warehouse clubs in three days.

The male suspect fired a handgun at his ex-girlfriend and her current boyfriend as they loaded shopping items into their car, Chula Vista Police Department Lt. Dan Peak told USA TODAY.

The suspect died from self-inflicted gunshot wounds about an hour after he opened fire. The man and woman are undergoing surgery for serious injuries, Peak said. The woman's infant, who sat in a nearby stroller during the shooting, was not injured.

Monday's shooting occurred in the city of Chula Vista in San Diego County, about 100 miles from the site of Friday's shooting in Corona that killed one man and injured two others. Corona Police are now reviewing video footage of the incident.

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Peak said the Chula Vista suspect approached the couple from behind. The extent of a conversation prior to the shooting is unclear, Peak said, based on varying witness interviews.

Chula Vista resident Angela Shelton told the San Diego Union-Tribune she initially thought the female victim had a heart attack when she saw her clutch her chest. From the passenger seat of a truck backing out of a parking spot, Shelton saw a man go to help her.

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But then she saw him suffer a gunshot wound, Shelton told the newspaper. The gunman then fired repeatedly at the couple and bullets punctured the truck.

“I could have been shot, too,” she told the Union-Tribune. “It’s very scary.”

Chula Vista police received several reports about the parking lot shooting just before 1 p.m. Police are investigating what motivated the shooting, Peak said.

Interviews with family members confirmed the suspect and female victim previously had a dating relationship, Peak said, but the length of the relationship is unclear. Investigators plan to interview the female victim when she is in stable condition.

Contributing: The Associated Press