South Dakota has been put on alert as authorities ramp up their search for the suspect who shot and killed one Minnesota lawmaker and her husband, and wounded a second lawmaker and his wife early Saturday.

Sen. Amy Klobuchar, D-Minn., told NBC’s “Meet the Press” on Sunday that while authorities believe the suspect, 57-year-old Vance Luther Boelter, could still be in Minnesota, they’re asking residents in South Dakota to be on the lookout.

“They’ve also put an alert out in South Dakota,” Klobuchar said, adding that the suspect is still believed to be in the Midwest.

Boelter is accused of shooting and killing former Minnesota House Speaker Melissa Hortman and her husband, Mark, in their Brooklyn Park home early Saturday. State Sen. John Hoffman, also a Democrat, and his wife, Yvette, were shot and wounded in their Champlin home about nine miles away.

Authorities have said the lawmakers were targeted.

The FBI shared images of Boelter appearing to impersonate a police officer and wearing a mask while on the doorstep of one of the lawmaker’s homes. A second photo shows him wearing a tan cowboy hat at a Minneapolis business shortly after the shootings.

The FBI named Boelter to its most wanted list and is offering a $50,000 reward for information that leads to Boelter’s arrest and conviction.

Fox News’ Danielle Wallace, Michael Dorgan and Julia Bonavita contributed to this report.