San Diego police shot and killed a fleeing robbery suspect late Monday morning after he took a hostage, holding a knife to the victim’s neck in the Morena area, authorities said.

Three officers opened fire on the suspect. The hostage was not hit, said sheriff’s Lt. Michael Krugh. The Sheriff’s Department is handling the investigation under a countywide protocol designed to prevent departments from investigating shootings by their own officers or deputies.

The suspect — who officers shot with a stun gun before he took the hostage — died at the scene of the shooting, which happened on a stretch of Friars Road closed for construction near Interstate 5. Krugh said he had not been identified but appeared to be in his 20s.

The incident started about 10:40 a.m. when San Diego police responded to a reported robbery at a store on Morena Boulevard north of Friars Road.

According to Krugh, a man carrying merchandise walked up to a store employee and asked if the store accepted credit cards. She told the man it did and headed behind the counter to ring up his purchases.

But the man started to walk out without paying but still carrying the items. The clerk tried to stop him, but he pulled out a knife and threatened her, Krugh said.

Officers quickly arrived and found the man on nearby Napa Street. Krugh said they tried to stop him, but he refused to give up.

“They could see that he had what looked like two knives still on him,” Krugh said.

The officers shot him with a Taser stun gun but it “had no effect on him,” Krugh said. The suspect instead ran to a homeless encampment off Friars Road, where he grabbed a man and held a knife to his neck, Krugh said.

Three officers opened fire and the suspect went down. Officers began to perform life-saving measures until medics arrived and took over, but the man died.

Authorities have not released the name of the man who died. The names of the officers were not released, but two of them are patrol officers assigned to Western Division and the third is assigned to San Diego Police Departments Neighborhood Policing Team.

One of the officers has been with the department for 12 years, another has been with the department for more than six years, according to Krugh. The other started with the department a year and a half ago.

It was the second officer-involved shooting in San Diego within 12 hours. On Sunday night, a San Diego police officer shot and wounded a man who allegedly threatened his girlfriend with a gun and then took the couple’s 11-month-old daughter, sheriff’s officials said.