(CNN)-- Someone who may be posing as a police officer is pulling cars over on Mississippi highways and then shooting drivers dead, authorities said.
After two such shootings this month, the Mississippi Bureau of Investigation is asking for the public's help to find the person.
The agency is receiving leads and processing forensic evidence, bureau spokesman Warren Strain said Tuesday.
"There are some similarities between the two incidents, mainly the fact they happened alongside a Mississippi highway," said MBI director Lt. Col. Larry Waggoner on Monday. "The concern is that someone is posing as a law enforcement officer and that is how these vehicles end up on the side of the road."
The first shooting occurred on May 8. Thomas Schlender, 74, was found dead about 1:30 a.m. in his car in the median of southbound Interstate 55 in Panola County.
On Friday, Lori Anne Carswell, 48, was found dead outside her car on the shoulder of Mississippi State Highway 713, in Tunica County, about 2:15 a.m.
The shootings took place about 55 miles apart, and the victims did not know each other, authorities said.
Authorities are asking citizens to be careful if they are pulled over and feel uneasy.
They advise drivers to call 911 and verify that a legitimate officer is pulling them over or drive to a well-lit, crowded place before stopping, actions permitted under Mississippi state law.