SAN DIEGO - In an interview with 10News from his jail cell, a man accused of robbing three local banks revealed the reason he said he committed the crimes.

Roberto Sepulveda, 24, was arrested Monday night in the front yard of his grandparents' home in Imperial Beach. Police said Sepulveda fled to the home after robbing a Navy Federal Credit Union in Egger Highlands that afternoon.

The bank robbery was Sepulveda's third, police said, and he told 10News it was just something he decided to do one day.

"So you didn't need any money and decided to rob three banks?" asked 10News reporter Dan Haggerty.

"Yeah," Sepulveda responded.

"Explain that to me," said Haggerty.

"Yeah, I just felt like doing it, just something to do," Sepulveda replied.

According to Sepulveda, he carried out the robberies with variations of a fake bomb that he constructed himself, using "a cardboard box, some duct tape, some Super Glue and some wires."

"And you said this is going to be my fake bomb?" asked Haggerty.

"Pretty much," said Sepulveda.

Sepulveda said he used his fake bomb to rob a Chase Bank in Imperial Beach and an AmericanWest Bank in Point Loma.

Sepulveda told 10News it was when he held up the Navy Federal Credit Union that he messed up. He said the FBI was watching him, and agents even called him to tell him so.

However, he said he robbed the bank anyway, even though he was a member of the bank.

"They [the FBI] followed me to the bank. They waited for me to do that. Then they followed my home … I actually have an account at that credit union. I just passed a note," said Sepulveda.

"You belong to that bank?" asked Haggerty.

"Yeah," said Sepulveda.

"Weren't you afraid they'd recognize you?" Haggerty asked.

"Not really, no," Sepulveda said.

"Had you been in there before?" asked Haggerty.

Sepulveda responded, "Not for a long time."

Sepulveda said he stole about $4,000 at each of the first two banks.

However, he said police arrested him before he could count the money from the Navy Federal Credit Union heist.