The shootings happened in four southeastern Michigan counties last week. The first occurred Oct. 16 and the last was reported Thursday. No injuries have been reported.
Ingham County Sheriff Gene Wriggelsworth told reporters after a task force meeting in East Lansing that the group's work is an example of "law enforcement at its best."
But he said the nature of the shootings makes the investigation a challenging one.
"We've got a 100-mile crime scene there, folks," Wriggelsworth said.
Investigators have linked at least seven of the shootings based on bullet fragments or casings found at the scenes, Oakland County Sheriff Michael Bouchard told The Associated Press. He said the information can't prove a specific weapon was used in all the shootings but said evidence points to a 9 mm semiautomatic handgun.
Most of the shootings involved cars near Interstate 96, and 10 of them were in Wixom.
Based on reports, authorities said the gunman appears to be a man in his 30s. A sketch of a possible suspect has been released.
So far, investigators have received at least 20 tips, Bouchard said.