BOSTON — An Alabama man caught with a loaded handgun in his carry-on bag at Boston’s Logan International Airport told Transportation Security Administration officers he didn’t know he had the weapon in his luggage and said a co-worker may have put it there, the TSA said in a statement Wednesday. The 9mm gun loaded with five bullets was spotted by a TSA X-ray machine at a security checkpoint on Tuesday, the agency said. The TSA contacted state police, who confiscated the gun and cited the man on a state weapons charge.