The incident happened around 11 a.m. Thursday when a robbery was reported at the Saehan Bank in the area of Beach Boulevard and Rosecrans Avenue.
A 911 caller told authorities that someone at the bank had a gun. Buena Park Police Chief Corey Sianez said the suspect made it clear to negotiators that he would kill himself and his hostage if he didn't get what he wanted.
Myung Jae Kim, 54, allegedly wanted $250,000. Police say he was armed with a sawed-off shotgun and four pipe bombs, one of which was in his back pocket.
After a four-hour standoff, officers opened fire, wounding him and rescuing the hostage, a female bank manager. Investigators said Kim had a personal dispute with the manager, who used to work at a different bank.
Police on Monday asked the district attorney to file charges, including attempted murder. Kim remains in critical condition.