DIAMONDHEAD (AP) — A man who helped a woman with car trouble on Interstate 10 on Monday night later stabbed the woman’s boyfriend in what he told authorities was self defense, sheriff’s officials said.

Matthew Danko, 45, of Kiln faces a charge of aggravated assault.

The stabbing occurred late Monday at the Circle K gas station in Diamondhead. Hancock County sheriff’s investigators are trying to determine whether Danko’s use of force was justified, Chief Investigator Glenn Grannan said.

A woman ran out of gas on I-10 shortly before midnight and tried calling her boyfriend for help but could not get in touch with him, Grannan said.

Danko, who was also traveling on I-10, spotted the stranded motorist and pulled over to lend assistance. He gave the woman a ride to a gas station at the Delisle exit, where they purchased and filled up a gas can, Grannan said.

At some point on the way back to the woman’s car, the woman’s boyfriend, later identified as Vance Starita, pulled up behind them on I-10 and tried to get Danko to pull over.

Grannan said Danko refused to stop on the side of the interstate and instead pulled into the Diamondhead exit and stopped at the Circle K.

This apparently angered Starita, and the two men got into an argument that turned physical. In the middle of the fight, Danko pulled a pocket knife and stabbed Starita in the back, Grannan said.

Starita was taken to Hancock Medical Center for treatment of non-life threatening injuries.

Danko told investigators he stabbed Starita in self-defense, Grannan said.

“(Danko) says the guy had him in a headlock so he had to stab him to get him off,” he said. “But the boyfriend says (Danko) had him in a headlock.”

Danko was booked into the Hancock County jail, then released Wednesday on a bond of $5,000, reduced from an initial $100,000.