Homemade Firearm Used to Kill MP

I've sure you've seen the reports of the shooting and stabbing attack that resulted in Jo Cox's death. Cox was a Member of Parliament (MP) that had been campaigning against Brexit. A report from the Daily Mail indicates that a witness to the attack described the firearm used as "looking homemade." Other witnesses indicate that it looked old fashioned, like a musket (although it was pistol sized, not a long-arm).