A Montana Highway Patrol trooper who was investigating an earlier shooting was himself shot and critically injured early Friday after finding the suspect's vehicle, leading authorities to launch an overnight manhunt that ended in the arrest of a 29-year-old man, officials said.

Another trooper found Wade Palmer, 35, wounded and still buckled into his patrol car outside a bar in the small town of Evaro, a statement from Montana Highway Patrol officials said. The shooter had fled.

Palmer was taken to a Missoula hospital, where he was listed in critical condition. Police shut down that stretch of U.S. Highway 93, warned residents to lock their doors and then spent hours searching before they arrested Johnathan Bertsch at about 6:15 a.m.

Bertsch was being held as a suspect in both Palmer's shooting and the earlier shooting about 10 miles (16 kilometers) away in Missoula, where two men and a woman sitting in a car were wounded late Thursday, said Missoula County Chief Deputy Attorney Jason Marks.

No other suspects were being sought in the shootings. Charges were expected to be filed against Bertsch Friday afternoon, and he was expected to make an initial court appearance on Monday, Marks said. There was no immediate information on whether he has a lawyer to speak on his behalf.

The three people from the first shooting outside a car dealership were taken to a hospital for gunshot wounds, Missoula police Sgt. Travis Welsh told the Missoulian newspaper. Their conditions weren't immediately clear.

Palmer has been a trooper since 2012. He has a wife and two children, and he won the law enforcement agency's highest honor, the Medal of Valor, in 2015.

Bertsch was previously arrested in 2009 for allegedly stealing gas, then leading officers on a chase and ramming his car into a patrol car, the Missoulian reported.