French authorities are worried they might have a serial killer on their hands. A woman was shot four times in the head in Paris on Thursday, a killing that shows similarities to three other murders in the capital since November. Though authorities wouldn’t confirm that they think the killings are the work of one person, they did acknowledge that they may be related. “On the theory of a serial killer, I will simply say that three of the murders — the second, third and fourth, show similarities,” Interior Minister Claude Guéant said in a radio interview. The Guardian reports that the killings have been linked to a 7.65mm gun. Thursday’s killer was seen fleeing the scene of the crime on a motorcycle, similar to Mohammed Merah, the self-proclaimed Al Qaeda fighter, who was shot and killed by police in Toulouse after killing seven the day before. Police did stress that they’ve yet to link the Paris killings to terrorism though.