(GRAND RAPIDS, Mich.) — Joseph Alexander uses magnets to fish for valuables in lakes and rivers, but on Tuesday, he pulled something he never expected out of the Grand River in Grand Rapids. It was a live World War I grenade.

“As scary as it is, it’s equally exciting,” said Alexander, “and I’m glad that I was the one that pulled it out. I’m glad nothing bad happened. I’m glad it didn’t explode in the river or in my hand. Or in the car. But I do think it’s a really cool thing to find.” He also said he was surprised to find something like that so close to the city.

Alexander called police, who will use C-4 to safely detonate it. He hopes they’ll let him keep of few prices for himself.

He’s posted his story and more photos of the century-old artifact to his Facebook page.