Story highlights Authorities analyze leads and forensic evidence

Authorities believe two separate shootings are linked

The shootings occurred about 55 miles apart

"The concern is that someone is posing as a law enforcement officer," an official says

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 was receiving leads and processing forensic evidence, bureau spokesman Warren Strain said Tuesday.

John Champion, district attorney for the state's 17th District, said there were no good descriptions of a vehicle.

"Both of the shootings occurred in very remote areas," Champion told HLN's Vinnie Politan.

Authorities were 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.

"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," said MBI director Lt. Col. Larry Waggoner.

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.