MIAMI SPRINGS, Fla. -- Police said a man attempted to rob the Washington Mutual bank at 4475 NW 36th St. with a BB gun Tuesday morning.

Miami Springs police were alerted to a silent alarm triggered at the Washington Mutual at 9:13 a.m. Officers working a detail four blocks away surrounded the bank in a minute and a half.

"The gunman came in yelling and cussing," said Carlos Ardeaga, a customer inside the bank during the robbery. "He told everyone to lie down on the floor and said not to call the police or he would start shooting."

Police said the gunman demanded more than $50,000 in cash from the teller and was exiting the bank with the money when he noticed police with their guns drawn and the bank surrounded.

"Upon seeing the officers surround the bank, he went back in and threatened bank employees and patrons," Miami Spring police Lt. Dan Kelly said.

Ardeaga told Local 10's Todd Tongen it was at that time that he feared for his life.

"He wanted to know who called the cops," said Ardeaga. "He said they ruined his life and if he was going down, he wasn't going down alone."

The gunman eventually surrendered and was taken into custody.

Luis Martinez is charged with armed robbery, use of a firearm in the commission of a felony and numerous counts of false imprisonment. Police said Martinez used a BB gun replica of a semiautomatic handgun.