A Michigan woman drowned herself and her twin daughters by intentionally driving into the Kalamazoo River, authorities said Tuesday.

Two other girls were in the car with the 44-year-old woman, but she let them out before she drove into the water in Kalamazoo on Monday, the city Department of Public Safety’s chief said.

Searchers found the submerged car near a park in the city Monday night and discovered the bodies of the woman and one of her daughters, authorities said.

They found the other girl’s body Tuesday morning after more searching in the river, police said.

The relationship of the two girls who survived to the woman was not released.

“This is just a tragedy for our community,” public safety chief Karianne Thomas said.

Thomas added that police are working to find a motive and nail down a timeline before the woman drove into the river.

“It’s a question here in Kalamazoo that we’re all asking,” she said of why the woman killed her two daughters. “We don’t have an answer.”