A great-grandmother walked into the gun buyback event at True Bethel Baptist Church on Saturday with a long object wrapped in a dark trash bag and her teenage grandson at her side.

She handed the package to a police officer.

“Whoa,” he gasped under his breath as he unwrapped it. “AK.”

It was a civilian model AK-47, a semiautomatic assault rifle.

The woman said that about a year ago, a young man being chased by the police dropped it in her yard.

“I didn’t know what to do with it so I just kept it,” the woman said, declining to give her name. “I’m scared of these things. . . . I’m glad it’s gone.”

Saturday, she and hundreds of other people across the city — and beyond — turned in unwanted guns during the city’s second gun buyback event.

Mayor Byron W. Brown gathered with other city officials Saturday night in the firing range at Police Headquarters. They were surrounded by guns turned in by people who visited seven churches that served as drop-off sites. The weapons included Uzis, double-barreled shotguns, sawed-off shotguns and even a small-caliber zip gun. The latter looks like a pen and can be placed in a lapel for easy concealment.

“We have quite a few nasty weapons,” First Deputy Commissioner Byron C. Lockwood said. A final weapons audit will be performed in the coming days, but Richard F. Calipari, deputy comptroller for investment and debt management, released tentative figures that totaled 720 weapons. Calipari said 261 handguns, 220 rifles, 234 non-functioning guns and five assault weapons were turned in.

In return, those surrendering the weapons received prepaid cash cards of varying amounts, depending on the type of gun. Calipari said $33,415 in cash cards were issued, an expense that is being financed through the assets of drug seizures and other crimes.

Assault weapons, such as the one the great-grandmother turned in, received the highest amount — $100. Handguns fetched $75, rifles and shotguns got $50 and nonworking

or antique guns as well as BB guns and starter pistols, $10.

Last year, at the first buyback, the city collected 878 guns, 599 of them functioning weapons. While 18 percent fewer guns were turned in this year, Brown said he was pleased with the results. He noted the first initiative was promoted for a longer period of time.

The weapons will be destroyed as part of the city’s “no questions asked” pledge during the gun buyback. No weapons will be tested to see if they were used in prior crimes.

Earlier Saturday, Brown kicked off the buyback at St. John Baptist Church on Goodell Street.

“There are too many guns on the streets of our city,” he said. “There have been too many senseless homicides, particularly among young people in the city.”

Police Commissioner H. Mc- Carthy Gipson encouraged citizens to participate.

“It’s good for the City of Buffalo. It’s good for the citizens. It’s good for our families. We never know: It prevents [the guns] from falling into undesirable hands and could potentially save a life.”

Brown, noting that one man turned in 13 functioning handguns, said if a burglar had raided the man’s house, there would have been more than a dozen illegal weapons on the streets. And Gipson noted the gun used to shoot Officer Patricia Parete, who was left paralyzed, had been stolen in a burglary years earlier.

Many studies conducted over the years suggest gun buy-backs aren’t effective in reducing crime and serve as little more than photo opportunities for politicians.

Brown disagreed.

“I don’t know what studies say but I know that in the City of Buffalo there have been 31 people killed by homicide [this year] . . . We want to do anything that we can, use any tactic, every strategy that we can to stop this senseless violence.”

Buyback participants were supportive of the event Saturday.

Roger Walter, 57, of Cheektowaga brought in four pistols to St. Thomas Aquinas Church on Abbott Road, where a line of people waited to turn in their guns. He had a permit for his guns but decided he didn’t want them anymore.

“In our neighborhood, we’ve had a few burglaries,” said Walter, who was afraid they could be stolen.

A 37-year-old Cheektowaga woman came with her mother to turn in her father’s old handgun.

“This is great if the right people turn them in,” she said. “But the people who should be turning them in aren’t.”