Grant Anderson, 52, of Santa Cruz, was spotted leaving Bank of the West at 1551 Pacific Ave. at about 11 a.m., police Lt. Larry Richard said.
At the same time, employees and customers noticed two suspicious-looking pieces of luggage left in the bank and notified police, Richard said.
Responding officers the Santa Cruz County sheriff's bomb squad cordoned off the 1500 block of Pacific Avenue to investigate the luggage just before noon.
At about that time, traffic was rerouted near the bank, impacting drivers moving through Front, Water, Center, and Mission streets, police said.
During the bomb squad's initial assessment, Anderson returned to the bank inquiring about his suitcases, Richard said.
"He described the bags to a T," he said.
Police allowed Anderson to get his bags just before arresting him for trespassing, Richard said.
"For us, it seemed like he purposely left the bags there," Richard said. "He didn't look apologetic."
Anderson, who has a prior criminal history, was arrested on a misdemeanor charge of trespassing and later released.
The charge stipulates a person is committing a crime by intentionally interfering with any lawful business, which police believed Anderson did.
"He has a history of trespassing in places and interfering with businesses, and he is not a bank customer there," Richard said.
The bank was closed for about 3 hours.
A bank manager declined to comment about the situation.