2 Youths Held, 2 Sought in Foiled Bank Holdup : Crime: The attempted robbery occurs close to the scene of another heist this week in Mission Viejo.

MISSION VIEJO — Two teen-agers with semi-automatic handguns escaped empty-handed from a bank robbery Thursday after a packet of dye slipped in with the stolen cash exploded in their backpack, police said.

The robbery occurred on the same street and only several blocks from a bank that was robbed on Monday. That robbery occurred less than an hour before a former police officer, himself suspected of a dozen bank robberies, was shot to death in a Mission Viejo parking lot by FBI agents.

“Yes, I would say we’ve had an unusual week,” said Orange County Sheriff’s Lt. Kim Markuson, a bank robbery investigator.

About 10 a.m. Thursday, two teen-agers brandishing semi-automatic handguns entered La Jolla Bank in the 24300 block of Alicia Parkway, jumped over the counter and demanded that the tellers hand over cash from the bank’s vault, investigators said. The amount taken was not disclosed by bank officials.

As the robbers fled out the door, their cash-filled backpack exploded, spewing red dye on the pavement but apparently not on the robbers, Markuson said.

They fled in two cars, which were waiting in the parking lot with drivers, Sheriff’s Lt. Jay Mendez said.

The descriptions of the cars, both Ford Thunderbirds, were broadcast on all police channels, and Tustin police officers later located one of the cars heading north on the Santa Ana Freeway near West Main Street, Mendez said.

Two youths apparently from Los Angeles were booked into Juvenile Hall on suspicion of armed robbery. The youths said they were 17, but investigators had not verified that Thursday. Two other suspects were still being sought, Mendez said.

Three days earlier, a man in his 50s entered a Wells Fargo Bank a few blocks away on the same street and handed a teller a note demanding cash, sheriff’s detectives said. The man, who apparently was armed, walked off with $490, according to investigators.

“There was very little commotion,” bank spokeswoman Kathleen Shilkret said. “Nobody other than the teller even knew what happened.”

The assailant was still being sought Thursday, according to investigators.

On Monday, former Fountain Valley police officer Kevin D. Arnold, suspected of robbing banks in Orange and San Diego counties, was shot to death when he reportedly resisted arrest by federal agents in the parking lot of the Portola Plaza.